blog: we already have go 2
Signed-off-by: Xe Iaso <me@christine.website>
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title: We Already Have Go 2
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date: 2022-05-25
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tags:
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- golang
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- generics
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- context
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- modules
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---
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I have been using Go since Go 1.4. Since I started using Go so long ago, I’ve
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seen the language evolve significantly. The Go I write today is roughly the same
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Go as the Go I wrote back when I was still learning the language, but overall
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it’s evolved and changed into something similar yet different feeling in
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practice. Thinking back over the years, here are some of the biggest ticket
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items that stand out for me:
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* The compiler rewrite in Go
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* Go modules
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* The context package
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* Generics
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This is a good thing. Go has had a lot of people use it. My career would not
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exist in its current form without Go. My time in the Go community has been
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_catalytic_ to my career goals and it’s made me into the professional I am
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today. Without having met the people I did in the Go slack, I would probably not
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have gotten as lucky as I have as consistently as I have.
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Releasing a “Go 2” has become a philosophical and political challenge due to the
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forces that be. “Go 2” has kind of gotten the feeling of “this is never going to
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happen is it” with how the political forces within and without the Go team are
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functioning. They seem to have been incrementally releasing new features and
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using version gating in `go.mod` to make it easier on people. This is pretty
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great and I am well in favour of this approach, but with all of the changes that
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have built up there really should be a Go 2 by this point. If only to make no
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significant changes and tag what we have today as Go 2.
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<xeblog-conv name="Cadey" mood="coffee">Take everything I say here with a grain
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of salt the size of east Texas. I am not an expert in programming language
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design and I do not pretend to be one on TV. I am also not a member of the Go
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team nor do I pretend to be one or see myself becoming one in the
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future.</xeblog-conv>
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## The Compiler Rewrite in Go
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When the Go compiler was first written, it was written in C because the core Go
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team has a background in Plan 9 and C was its lingua franca. However as a result
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of either it being written in C or the design around all the tools it was
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shelling out to, it wasn’t easy to cross compile Go programs. If you were
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building windows programs on a Mac you needed to do a separate install of Go
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from source with other targets enabled. This worked, it wasn’t the default
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though and eventually the Go compiler rewrite in Go changed this so that Go
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could cross compile natively with no effort required.
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<xeblog-conv name="Cadey" mood="enby">This has been such an amazingly productive
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part of the Go toolchain that I was shocked that Go didn’t have this out of the
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gate at version 1. Most people that use Go today don’t know that there was a
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point where Go didn’t have the easy to use cross-compiling superpower it
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currently has, and I think that is a more sure marker of success than anything
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else.</xeblog-conv>
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## Go Modules
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In Go's dependency model, you have a folder that contains all your Go code
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called the GOPATH. The GOPATH has a few top level folders that have a well-known
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meaning in the Go ecosystem:
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* bin: binary files made by `go install` or `go get` go here
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* pkg: intermediate compiler state goes here
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* src: Go packages go here
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GOPATH has one major advantage: it is ruthlessly easy to understand the
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correlation between the packages you import in your code to their locations on
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disk.
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If you need to see what `within.website/ln` is doing, you go to
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GOPATH/src/within.website/ln. The files you are looking for are somewhere in
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there. You don’t have to really understand how the package manager works (mostly
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because there isn’t one). If you want to hack something up you just go to the
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folder and add the changes you want to see.
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You can delete all of the intermediate compiler state easily in one fell swoop.
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Just delete the `pkg` folder and poof, it’s all gone. This was great when you
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needed to free up a bunch of disk space really quickly because over months the
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small amount of incremental compiler state can really add up.
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The go compiler would fetch any missing packages from the internet at build time
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so things Just Worked™️. This makes it utterly trivial to check out a project and
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then build/run it. That combined with `go get` to automatically just figure
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things out and install them made installing programs written in Go so easy that
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it’s almost magic.
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It was conceptually simple to reason about. Go code goes in the GOPATH. The best
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place for it was in the GOPATH. There's no reason to put it anywhere else.
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Everything was organized into its place and it was lovely.
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This wasn’t perfect though. There were notable flaws in this setup that were
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easy to run into in practice.
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There wasn't a good way to make sure that everyone was using the _same copies_
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of every library. People did add vendoring tools later to check that everyone
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was using the same copies of every package, but this also introduced problems
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when one project used one version of a dependency and another project used
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another in ways that were mutually incompatible.
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The process to get the newest version of a dependency was to grab the latest
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commit off of the default branch of that git repo. There was support for SVN,
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mercurial and fossil, but in practice Git was the most used one so it’s almost
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not worth mentioning the other version control systems. This also left you at
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the mercy of other random people having good code security sense and required
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you to audit your dependencies, but this is fairly standard across ecosystems.
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Dependency names were case sensitive on Linux but not on Windows or macOS.
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Arguably this is a "Windows and macOS are broken for backwards compatibility
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reasons" thing, but this did bite me at random times without warning.
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The default location for the GOPATH created a folder in your home directory.
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<xeblog-conv name="Cadey" mood="coffee">Yeah, yeah, this default was added later
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but still people complained about having to put the GOPATH somewhere at first.
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Having to choose a place to put all the Go code they would use seemed like a big
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choice that people really wanted solid guidance and defaults on. After a while
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they changed this to default to `~/go` (with an easy to use command to influence
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the defaults without having to set an environment variable). I don't personally
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understand the arguments people have for wanting to keep their home directory
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"clean", but the arguments are valid regardless.</xeblog-conv>
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If the wrong random people deleted their GitHub repos, there's a chance your
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builds could break unless your GOPATH had the packages in it already. Then you
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could share that with your coworkers or the build machine somehow, maybe even
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uploading those packages to a git repository to soft-fork it.
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Overall I think GOPATH was a net good thing for Go. It had its downsides, but as
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far as these things go it was a very opinionated place to start from. This is
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something typical to Go (much to people's arguments), but the main thing that it
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focused on was making Go conceptually simple. There's not a lot going on there.
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You have code in the folder and then that's where the Go compiler looks for
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other code. It's a very lightweight approach to things that a lot of other
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languages could learn a lot from. It's great for monorepos because it basically
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treats all your Go code as one big monorepo. So many other languages don’t
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really translate well to working in a monorepo context like Go does.
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That making sure everyone had the same versions of everything problem ended up
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becoming a big problem in practice. I'm assuming that the original intent of the
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GOPATH was to be similar to how Google's internal monorepo worked, where
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everyone clones and deals with the entire GOPATH in source control. You'd then
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have to do GOPATH juggling between monorepos, but the intent was to have
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everything in one big monorepo anyways, so this wasn't thought of as much of a
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big deal in practice. It turns out that people in fact did not want to treat Go
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code this way, in practice this conflicted with the dependency model that Go
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encouraged people to use with how people consume libraries from GitHub or other
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such repository hosting sites.
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The main disconnect between importing from a GOPATH monorepo and a Go library
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off of GitHub is that when you import from a monorepo with a GOPATH in it, you
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need to be sure to import the repository path and not the path used inside the
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repository. This sounds weird but this is the difference between importing
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`github.com/Xe/x/src/github.com/Xe/x/markov` and `github.com/Xe/x/markov`. This
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means that things need to be extracted _out of_ monorepos and reformatted into
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“flat” repos so that you can only grab the one package you need. This became
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tedious in practice.
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In Go 1.5 (the one where they rewrote the compiler in Go) they added support for
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[vendoring code into your
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repo](https://medium.com/@freeformz/go-1-5-s-vendor-experiment-fd3e830f52c3).
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The idea here was to make it easy to get closer to the model that the Go authors
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envisioned for how people should use Go. Go code should all be in one big happy
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repo and everything should have its place in your GOPATH. This combined with
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other tools people made allowed you to vendor all of your dependencies into a
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`vendor` folder and then you could do whatever you wanted from there.
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One of the big advantages of the `vendor` folder was that you could clone your
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git repo, create a new process namespace and then run tests without a network
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stack. Everything would work offline and you wouldn't have to worry about
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external state leaking in. Not to mention removing the angle of someone deleting
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their GitHub repos causing a huge problem for your builds.
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<xeblog-conv name="Mara" mood="happy">Save tests that require internet access or
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a database engine!</xeblog-conv>
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This worked for a very long time. People were able to vendor their code into
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their repos and everything was better for people using Go. However the most
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critical oversight with the `vendor` folder approach was that the Go team didn't
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create an official tool to manage that `vendor` folder. They wanted to let tools
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like `godep` and `glide` handle that. This is kind of a reasonable take, Go
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comes from a very Google culture where this kind of problem doesn't happen, so
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as a result they probably won't be able to come up with something that meets the
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needs of the outside world very easily.
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<xeblog-conv name="Cadey" mood="enby">I can't speak for how `godep` or `glide`
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works, I never really used them enough to have a solid opinion. I do remember
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using [`vendor`](https://github.com/bmizerany/vendor) in my own projects though.
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That had no real dependency resolution algorithm to speak of.</xeblog-conv>
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After a while the Go team worked with people in the community to come up with an
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"official experiment" in tracking dependencies called `dep`. `dep` was a tool
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that used some more fancy computer science maths to help developers declare
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dependencies for projects in a way like you do in other ecosystems. When `dep`
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was done thinking, it emitted a bunch of files in `vendor` and a lockfile in
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your repository. This worked really well and when I was working at Heroku this
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was basically our butter and bread for how to deal with Go code.
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<xeblog-conv name="Cadey" mood="enby">It probably helped that my manager was on
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the team that wrote `dep`.</xeblog-conv>
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One of the biggest advantages of `dep` over other tools was the way that it
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solved versioning. It worked by having each package declare
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[constraints](https://golang.github.io/dep/docs/the-solver.html) in the ranges
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of versions that everything requires. This allowed it to do some fancy
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dependency resolution math similar to how the solvers in `npm` or `cargo` work.
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This worked fantastically in the 99% case. There were some fairly easy to
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accidentally get yourself in cases where you could make the solver loop
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infinitely though, as well as ending up in a state where you have mutually
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incompatible transient dependencies without any real way around it.
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<xeblog-conv name="Mara" mood="hacker">`npm` and `cargo` work around this by
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letting you use multiple versions of a single dependency in a
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project.</xeblog-conv>
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However these cases were really really rare, only appearing in much, much larger
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repositories. I don't think I practically ran into this, but I'm sure someone
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reading this right now found themselves in `dep` hell and probably has a hell of
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a war story around it.
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This lead the Go team to come up with a middle path between the unrestricted
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madness of GOPATH and something more maximal like `dep`. They eventually called
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this Go modules and the core reasons for it are outlined in [this series of
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technical posts](https://research.swtch.com/vgo). Apparently the development of
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Go modules came out as a complete surprise, even to the core developer team of
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`dep`. I'm fairly sure this lead my manager to take up woodworking as his main
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non work side hobby, I can only wonder about the kind of resentment this created
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for other parts of the `dep` team.
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<xeblog-conv name="Cadey" mood="coffee">The `dep` team was as close as we've
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gotten for having people in the _actual industry_ using Go _in production_
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outside of Google having a real voice in how Go is used in the real world. I
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fear that we will never have this kind of thing happen again.</xeblog-conv>
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Go modules does solve one very critical problem for the Go ecosystem though: it
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allows you to have the equivalent of the GOPATH but with multiple versions of
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dependencies in it. It allows you to have `within.website/ln@v0.7` and
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`within.website/ln@0.9` as dependencies for _two different projects_ without
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having to vendor source code or do advanced GOPATH manipulation between
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projects. It also adds cryptographic checksumming for each Go module that you
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download from the internet. This allows you to avoid having to shell out to
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`git` every time you fetch a module that someone else has fetched before.
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Companies could run their own Go module proxy and then use that to provide
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offline access to Go code fetched from the internet.
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<xeblog-conv name="Mara" mood="hmm">Wait, couldn't this allow Google to see the
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source code of all of your Go dependencies? How would this intersect with
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private repositories that shouldn't ever be on anything but work
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machines?</xeblog-conv>
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<xeblog-conv name="Cadey" mood="coffee">Yeah, this was one of the big privacy
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disadvantages out of the gate with Go modules. I think that in practice the
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disadvantages are limited, but still the fact that it defaults to phoning home
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to Google every time you run a Go build without all the dependencies present
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locally is kind of questionable. They did make up for this with the checksum
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verification database a little, but it's still kinda sus.</xeblog-conv>
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The earliest version of Go modules basically was a glorified `vendor` folder
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manager. This worked out amazingly well and probably made prototyping this a
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hell of a lot easier. This worked well enough that we used this in production
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for many services at Heroku. We had no real issues with it and most of the
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friction was with the fact that most of the existing ecosystem had already been
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using `dep` or `glide`.
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If they had shipped this in prod, it probably would have been a huge success. It
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would also let people continue to use `dep`, `glide` and `godep`, but just doing
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that would also leave the ecosystem kinda fragmented. You’d need to have code
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for all 4 version management systems to parse their configuration files and
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implement algorithms that would be compatible with the semantics of all of them.
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It would work and the Go team is definitely smart enough to do it, but in
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practice it would be a huge mess.
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This also solved the case-insensitive filesystem problem with
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[bang-casing](https://go.dev/ref/mod#goproxy-protocol). This allows them to
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encode the capital letters in a path in a way that works on macOS and Windows
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without having to worry about horrifying hacks that are only really in place for
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Photoshop to keep working.
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However one of the bigger downsides that came with Go modules is what I've been
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calling the "v2 landmine" that Semantic Import Versioning gives you. One of the
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very earliest bits of Go advice was to make the import paths for version 1 of a
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project and version 2 of a project different so that people can mix the two to
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allow more graceful upgrading across a larger project. Semantic Import
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Versioning enforces this at the toolchain level, which means that it can be the
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gate between compiling your code or not.
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<xeblog-conv name="Cadey" mood="coffee">Many people have been telling me that
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I’m kind of off base for thinking that this is a landmine for people, but I am
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using the term “landmine” to talk about this because I feel like it reflects the
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rough edges of unexpectedly encountering this in the wild. It kinda feels like
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you stepped on a landmine.</xeblog-conv>
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The core of this is that when you create major version 2 of a Go project, you
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need to adjust all your import paths everywhere in that project to import the
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`v2` of that package or you will silently import the `v1` version of that
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package. This can end up making large projects create circular dependencies on
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themselves, which is quite confusing in practice. When consumers are aware of
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this, then they can use that to more gradually upgrade larger codebases to the
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next major version of a Go module, which will allow for smaller refactors.
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This also applies to consumers. Given that this kind of thing is something that
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you only do in Go it can come out of left field. The go router
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[chi](https://github.com/go-chi/chi/issues/462) tried doing modules in the past
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and found that it lead to confusing users. Conveniently they only really found
|
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this out after the Go modules design was considered final and Semantic Import
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Versioning has always been a part of Go modules and the Go team is now refusing
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to budge on this.
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<xeblog-conv name="Cadey" mood="coffee">My suggestion to people is to never
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release a version `1.x.x` of a Go project to avoid the “v2 landmine”. The Go
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team claims that the right bit of tooling can help ease the pain, but this
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tooling never really made it out into the public. I bet it works great inside
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google3 though!</xeblog-conv>
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Overall though, Go modules has been a net positive for the community and for
|
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people wanting to create reliable software in Go. It’s just such a big semantic
|
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break in how the toolchain works that I almost think it would have been easier
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to accept if _that_ was Go 2.
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<xeblog-conv name="Mara" mood="hmm">Wait, doesn’t the Go compiler have a
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backwards compatibility promise that any code built with Go 1.x works on go
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1.(x+1)?</xeblog-conv>
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<xeblog-conv name="Cadey" mood="coffee">Yes, but that only applies to _code you
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write_, not _semantics of the toolchain_ itself. On one hand this makes a lot of
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sense and on the other it feels like a cop-out. The changes in how `go get` now
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refers to adding dependencies to a project and `go install` now installs a
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binary to the system have made an entire half decade of tool installation
|
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documentation obsolete. It’s understandable why they want to make that change,
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but the way that it broke people’s muscle memory is [quite frustrating for
|
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users](https://github.com/golang/go/issues/40276#issuecomment-1109797059) that
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aren’t keeping on top of every single change in semantics of toolchains (this
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bites me constantly when I need to quick and dirty grab something outside of a
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Nix package). I understand _why_ this isn’t a breaking change as far as the
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compatibility promise but this feels like a cop-out.</xeblog-conv>
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## Contexts
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One of Go’s major features is its co-operative threading system that it calls
|
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goroutines. Goroutines are kinda like coroutines that are scheduled by the
|
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scheduler. However there is no easy way to "kill" a goroutine. You have to add
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something to the invocation of the goroutine that lets you signal it to stop and
|
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then opt-in the goroutine to stop. This ended up leading to the
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[context](https://pkg.go.dev/context) package being created in the standard
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library. A Go context lets you more easily and uniformly handle timeouts and
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giving up when there is no more work to be done.
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|
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Mara+hacker\ This started as something that existed inside the Google monorepo
|
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that escaped out into the world. They also claim to have an internal tool that
|
||||
makes [`context.TODO()`](https://pkg.go.dev/context#TODO) useful (probably by
|
||||
showing you the callsities above that function?), but they never released that
|
||||
tool as open source so it’s difficult to know where to use it without that added
|
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context.
|
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|
||||
- [ ] Examples of how to thread them in:
|
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- [ ] Basic example using a select statement and a timer to poll the context
|
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timeout vs the timer (let’s pretend the timer is some important but
|
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cancellable event that takes time to process)
|
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- [ ] HTTP request
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- [ ] Handling a control-C signal and cancelling a bunch of HTTP request
|
||||
|
||||
This is a huge benefit to the language because of how disjointed the process of
|
||||
doing this before contexts was. Trying to do this before contexts usually made
|
||||
you create a "stop channel" where you’d feed it a `bool` or a `struct{}{}` to
|
||||
signal that the other side doesn't need to care anymore. Because this wasn’t in
|
||||
the core of the language, every single implementation was different and required
|
||||
learning what the library did.
|
||||
|
||||
However I wish that the documentation was a bit more clear as to what they
|
||||
really offer and had some more examples of how to use them. Without context as
|
||||
to what contexts do, its documentation can kind of read [like
|
||||
this](https://christine.website/blog/vanbi-01-08-2019). This can make explaining
|
||||
what a context is to people kind of annoying.
|
||||
|
||||
<xeblog-conv name="Mara" mood="hacker">If you know Lojban, some of the satire in
|
||||
vanbi may be lost on you. Just pretend you don’t understand any of the words in
|
||||
there.</xeblog-conv>
|
||||
|
||||
I understand why they put data into the context type, but in practice I really
|
||||
wish they didn’t do that. This feature has been abused a lot in my experience.
|
||||
At Heroku a few of our production load bearing services used contexts as a
|
||||
dependency injection framework. This did work, but it turned a lot of things
|
||||
that would normally be compile time errors into runtime errors.
|
||||
|
||||
<xeblog-conv name="Cadey" mood="coffee">I say this as someone who maintains a
|
||||
library that uses contexts to store [contextually relevant log
|
||||
fields](https://pkg.go.dev/within.website/ln) as a way to make logs easier to
|
||||
correlate between.
Arguably you could make the case that people are misusing the
|
||||
tool and of course this is what will happen when you do that but I don't know if
|
||||
this is really the right thing to tell people.</xeblog-conv>
|
||||
|
||||
I wish contexts were in the core of the language from the beginning. I know that
|
||||
it is difficult to do this in practice (especially on all the targets that Go
|
||||
supports), but having cancellable syscalls would be so cool. It would also be
|
||||
really neat if contexts could be goroutine-level globals so you didn’t have to
|
||||
“pollute” the callsites of every function with them.
|
||||
|
||||
## Generics
|
||||
|
||||
One of the biggest ticket items that Go has added is "generic types", or being
|
||||
able to accept types as parameters for other types. This is really a huge ticket
|
||||
item and I feel that in order to understand _why_ this is a huge change I need
|
||||
to cover the context behind what you had before generics were added to the
|
||||
language.
|
||||
|
||||
One of the major standout features of Go is interface types. They are like Rust
|
||||
Traits, Java Interfaces, or Haskell Typeclasses; but the main difference is that
|
||||
interface types are _implicit_ rather than explicit. When you want to meet the
|
||||
signature of an interface, all you need to do is implement the contract that the
|
||||
interface spells out. So if you have an interface like this:
|
||||
|
||||
```go
|
||||
type Quacker interface {
|
||||
Quack()
|
||||
}
|
||||
```
|
||||
You can make a type like `Duck` a `Quacker` by defining the `Duck` type and a
|
||||
`Quack` method like this:
|
||||
|
||||
```go
|
||||
type Duck struct{}
|
||||
|
||||
func (Duck) Quack() { fmt.Println("Quack!") }
|
||||
```
|
||||
|
||||
But this is not limited to just `Ducks`, you could easily make a `Sheep` a
|
||||
`Quacker` fairly easily:
|
||||
|
||||
```go
|
||||
type Sheep struct{}
|
||||
|
||||
func (Sheep) Quack() { fmt.Println("*confused sheep noises*") }
|
||||
```
|
||||
|
||||
This allows you to deal with expected _behaviors_ of types rather than having to
|
||||
have versions of functions for every concrete implementation of them. If you
|
||||
want to read from a file, network socket, `tar` archive, `zip` archive, the
|
||||
decrypted form of an encrypted stream, a TLS socket, or a HTTP/2 stream they're
|
||||
all [`io.Reader`](https://pkg.go.dev/io#Reader) instances. With the example
|
||||
above we can make a function that takes a `Quacker` and then does something with
|
||||
it:
|
||||
|
||||
```go
|
||||
func main() {
|
||||
duck := Duck{}
|
||||
sheep := Sheep{}
|
||||
|
||||
doSomething(duck)
|
||||
doSomething(sheep)
|
||||
}
|
||||
|
||||
func doSomething(q Quacker) {
|
||||
q.Quack()
|
||||
}
|
||||
```
|
||||
|
||||
<xeblog-conv name="Mara" mood="hacker">If you want to play with this example,
|
||||
check it out on the Go playground [here](https://go.dev/play/p/INK8O2O-D01). Try
|
||||
to make a slice of Quackers and pass it to `doSomething`!</xeblog-conv>
|
||||
|
||||
You can also embed interfaces into other interfaces, which will let you create
|
||||
composite interfaces that assert multiple behaviours at once. For example,
|
||||
consider [`io.ReadWriteCloser`](https://pkg.go.dev/io#ReadWriteCloser). Any
|
||||
value that matches an `io.Reader`, `io.Writer` and an `io.Closer` will be able
|
||||
to be treated as an `io.ReadWriteCloser`. This allows you to assert a lot of
|
||||
behaviour about types even though the actual underlying types are opaque to you.
|
||||
|
||||
This means it’s easy to split up a [`net.Conn`](https://pkg.go.dev/net#Conn)
|
||||
into its reader half and its writer half without really thinking about
|
||||
it:
|
||||
|
||||
```go
|
||||
conn, _ := net.Dial("tcp", "127.0.0.1:42069")
|
||||
|
||||
var reader io.Reader = conn
|
||||
var writer io.Writer = conn
|
||||
```
|
||||
|
||||
And then you can pass the writer side off to one function and the reader side
|
||||
off to another.
|
||||
|
||||
There’s also a bunch of room for "type-level middleware" like
|
||||
[`io.LimitReader`](https://pkg.go.dev/io#LimitReader). This allows you to set
|
||||
constraints or details around an interface type while still meeting the contract
|
||||
for that interface, such as an `io.Reader` that doesn’t let you read too much,
|
||||
an `io.Writer` that automatically encrypts everything you feed It with TLS, or
|
||||
even something like sending data over a Unix socket instead of a TCP one. If it
|
||||
fits the shape of the interface, it Just Works.
|
||||
|
||||
- [ ] Show where that falls apart
|
||||
- [ ] The container package
|
||||
- [ ] Cloner
|
||||
- [ ] Viewer
|
||||
- [ ] Introduce Go generics
|
||||
- [ ] Overview of some of the types of collections it lets you make
|
||||
- [ ] Take a function with a slice `Duck`s or a slice of `Sheep` but not
|
||||
mixed `Duck`s and `Sheep`
|
||||
- [ ] This is a huge improvement to the language
|
||||
|
||||
---
|
||||
|
||||
We already have Go 2. It’s just called Go 1.18 for some reason. It’s got so many
|
||||
improvements and fundamental changes that I believe that this is already Go 2 in
|
||||
spirit. I, as some random person on the internet that is not associated with the
|
||||
Go team, think that if there was sufficient political will that they could
|
||||
probably label what we have as Go 2, but I don’t think that is going to happen
|
||||
any time soon. Until then, we still have a very great set of building blocks
|
||||
that allow you to make easy to maintain production quality services, and I don’t
|
||||
see that changing any time soon.
|
||||
Loading…
Reference in New Issue