Notes on Go

Despite having worked for so many years with colleagues who were major proponents (or even contributors) to Go/Golang, I’d somehow gone this long without having ever written a production grade service in the language, having only dabbled so far with toy projects, small scripts, and minor contributions to existing software. That all changed in the last few weeks, where I had the opportunity to assemble a pretty serious project in the language from scratch.

I took notes throughout the process so as not to lose my (relatively) fresh outlook on the language.

Building new programs requires typing a lot. The language is incredibly verbose and has few shortcuts. The upside is that once you have typed out that initial code, it’s eminently readable and relatively easy to maintain compared to many other languages.

All too often, the bar to understanding projects written in Ruby, Lisp, Haskell, Rust, C#, C++, or whatever, isn’t just figuring out the code, it’s also deciphering the localized (and often overcomplicated) abstractions that every developer ends up baking into their code to reduce line count, and in many cases that’s significant cognitive overhead. In Go that problem doesn’t exist to anywhere near the same extent.

After spending some time with them, I’m firmly convinced that green threads (Goroutines) and channels are the only way that concurrency should be exposed to developers.

When working in languages like Ruby (to pick an example of one that I’m very familiar with), even with experience, doing any work with concurrency is incredibly frustrating in just the sheer number of problems that you’re likely to run into. It’s tempting to think that this is because concurrency is inherently difficult, but it’s more to do with dull primitives that are error prone by default.

By comparison, when working in Go, it’s amazing how many programs you can write where your concurrent code will work perfectly the first time. I also find that even in cases where it doesn’t, it’s far more often due to a conceptual mistake that I’ve made than it is to a poorly designed language feature.

I also appreciate just how opinionated the Go team has been on this front. Other languages with strong concurrency stories like Haskell and Rust have opted to give users access to every type of primitive under the sun, and in the long run that tyranny of choice leads to an ecosystem of mixed ideas and no clear way forward.

Speed is absolutely critical, and not just for the runtime, but for the tooling. Being able to compile and run your entire test suite in under a second 1 changes the entire development experience in such a fundamental way that it’s hard to adequately describe. After working with a Go project for a while, going back to 10+ second iteration loops in languages like Ruby feels like trying to run a marathon while waist deep in a bog.

This is still a key place where Go stands apart even from other modern languages which tend to focus on runtime speed or sophisticated features while ignoring the development cycle 2.

But Go is also fast at runtime too. It’s nice to be able to write code in a high-level language and be able to trust that it will run quickly.

If every language was as easy to deploy as Go, Docker would never have been invented (maybe a slight exaggeration, but the need for it wouldn’t have been anywhere near as dire). Build a binary. Copy it to a target server. Stop the old service and bring the new one up. That’s it. No weird environment problems. No dependency headaches. No Bundler.

I now write all my throwaway scripts in Go for the same reason. If I ever need to run one with Cron, I know that I’m never going to have to deal with issues with $PATH or rbenv or anything else. Copy the executable to /usr/local/bin, inject it straight into my Crontab, and you’re done. killall even works; incredible.

There’s a lot to like about Go:

  • Defer: I love this abstraction. Although not quite as safe as something like a C# using block (in that you might accidentally remove the line and not notice), it’s far less cluttering.
  • Import: I’m firmly convinced now that importing packages with a short canonical identifier (e.g. fmt or http from “net/http”) and then having only one option for referencing that package in code is the One True Way. No more symbols with unknown and dubious origin (Haskell) or artisanal blends of qualified and non-qualified names (C#/Java/other).
  • Select: Although decisions like using default: to make a select blocking or non-blocking are a little obtuse, overall this construct is incredibly powerful.
  • Pipelines: By combining a few of the built-in language features, Go enables the construction of composable, scalable pipelines. This approach to parallelism is truly elegant and encourages developers to write programs that are more performant and which make better use of modern system resources (namely, more cores).
  • Labels: Incredibly useful for breaking out of an outer loop without introducing boilerplate. When used carefully, goto is also tremendously powerful (and comes with the perfect number of restrictions to prevent its abuse).
  • No metaprogramming and minimal OO: Sometimes the costs of what seem like good features on the surface outweigh their benefits. I’ll gladly write a little more code if it means that someone else will be able to understand it.
  • Static linking: Go didn’t invent this, but they did make it default. Static linking introduces some headaches in a few cases, but vastly improves the lives of the other 99% of users.
  • Standard library in Go: It’s an amazing feature to be able to check the implementation of core packages in the standard libraries. This isn’t all that unusual for newer languages these days, but it’s becoming increasingly harder to make the argument that languages like Ruby and Python that insist that having a standard library written in C is just fine.
  • Nice documentation features: Go has some neat innovations in documentation that solve real problems that are observable in almost every other language and framework. e.g. A locally runnable documentation server (great for flights), or testable examples, which mean that examples in documentation get run with the test suite so that they don’t fall out of date.

There were a lot of facets of Go that I read or heard about before trying and which I was pretty sure that I wouldn’t like. However, after using the language a while I quickly started warming up to them:

  • Dependency management: It took me a while to warm up to Go’s design around dependency management, but not having to run and manage everything through a slow and complex system like Bundler hugely improves the development experience. It also makes it very easy to jump into foreign libraries and examine their implementations when necessary.
  • Gofmt: Having a single convention for the language makes collaboration easier, and makes my own coding faster (in that I can rely on gofmt to correct certain things).
  • Errors on unused variables: These can be very annoying, but I can’t deny that these error messages have saved me from what would otherwise have been a bug multiple times now.
  • No generics: Having types only on special data structures like slices and maps gets you surprisingly far. Although not having generics does make using the language for certain things difficult, I was amazed after having built a multi-thousand LOC program to realize that I hadn’t wanted for them once.

I really did make an effort, but even so, some parts of the language are hard to love:

  • Error handling: I like that generally my programs don’t crash, but dealing with errors requires an incredible level of micro-management. Worse yet, the encouraged patterns of passing errors around through returns can occasionally make it very difficult to identify the original site of a problem.
  • The commmunity: Reading the mailings lists can be still be pretty depressing. Every critique of the language or suggestion for improvement, no matter how valid, is met with a barrage of either “you’re doing it wrongs”, or “only the Go core team that can have thoughts that are worth consideration” 3. Previously this level of zealotry had been reserved for holy crusades and text editors.
  • Debugging: gdb and pprof both work with Go, but with experiences that are rough enough around the edges that you’ll find yourself often resorting to print-debugging just to avoid the hassle.
  • Noisy diffs: The downside of gofmt is the possibility of noisy diffs. If someone adds a new field with a long name to a large struct, all the spacing changes and you end up with a huge block of red and a slow review 4.
  • Quirky syntax and semantics: Go is littered with quirky language syntax and semantics that are fine once you know them, but are unnecessarily opaque. Some examples:
    1. The distinction between new, make, and initialization with composite literals.
    2. Interfaces are always references.
    3. Symbols that start with capital letters are exported from packages.
    4. Channels created without a size are blocking.
    5. select blocks with a default case become non-blocking.
    6. You check if a key exists in a map by using a rare second return value of a normal lookup with square brackets.
    7. Named return values.
    8. Closing a channel causes any Goroutine that was listening on it to fall through having received a zero value of the channel’s type.
    9. Comparing interfaces to nil is allowed by the compiler, but apparently not a good idea, and can lead to some strange bugs.
  • JSON: Is as slow as reported due to its extensive use of reflection. This wouldn’t seem like it should be a problem, but can lead to surprising bottlenecks in otherwise fast programs.

There are very few parts of the language that are unapologetically bad, but that said:

  • Assertions: Although mostly palatable, the omission of a collection of meaningful assert functions (and the corresponding expectation that a custom-tailored message should be written every time you want to check that an error is nil) isn’t great to say the least.

The real problem though is that the unnecessary verbosity of tests acts as a natural deterrent to writing them, and projects with non-existent/poor/incomplete test suites are a dime a dozen. I’ve been using the testify require package to ease this problem, but there should be answer in the standard library.

Overall, I never quite reached the level of feverish passion for Go that many others have, but I consider it a thoroughly solid language that’s pleasant to work with. Furthermore, it may have reached the best compromise that we’ve seen so far in the landscape of contemporary languages in that it imposes constraints that are strong enough to detect large classes of problems during compilation, but is still fluid enough to work with that it’s easy to learn, and fast to develop.

1 Without tricks like Zeus that come with considerable gotchas and side effects.

2 e.g. Rust, or, and it hurts me to say this, Haskell.

3 The best single example of this that I’ve found so far is a request for a non-zero exit code in Golint. The community articulates the problem and shows an obvious demand and willingness to help. Meanwhile the member of Go core can’t manage to build even a single cohesive counterargument, but even so, the issue along with all its ideas and suggestions are summarily rejected.

Follow-up (2016/06/24): Russ Cox re-opened the issue (presumably after seeing complaints on Twitter given that the original maintainer had locked discussion on it) and it was subsequently resolved.

4?w=1 on GitHub to hide whitespace changes helps mitigate this problem, but isn’t the default, and doesn’t allow comments to be added.

Did I make a mistake? Please consider sending a pull request.