Managing Go Versions with direnv

Recently I've joined a project that requires previous version of Go. Since I have the latest version already installed on my machine I was looking for a way to manage different versions of Go in a single machine. In Python world, there is a very well-known version management called pyenv which is highly inspired by the Ruby's one: rbenv.

As for Go, it seems that there is no authoritative way to manage the versions of Go. Probably it is not a big issue as many would just upgrade to the latest version of the language since it essentially promises that new minor version of 1.X would not break the older ones. Yet, through a very brief Googling, I found that there are three main approaches for this problem:

1. Installing each version of Go from source. This article by Kale Blankenship describe the steps in details.
2. There is also a tool that is similar to pyenv and rbenv available in the Go ecosystem known as gvm It also comes with additional features such as managing different locations of GOPATH.
3. Lastly, we can also use go get. Yes! GO GET!

Installing a Different Version of Go

In this post, we will explore how to use go get to manage different versions Go. One small caveat for this approach is that not all Go versions are support. Supported versions are listed on the download page. Let's say that we need go1.8.7, all we have to do is:

$ go get golang.org/dl/go1.8.7
$ go1.8.7 download

Once the download is complete, we can compile our source code with v1.8.7 using

$ go1.8.7 version
go version go1.8.7 darwin/amd64
$ go1.8.7 build

Uninstalling can be done by removing the GOROOT directory:

$ rm -rf "$(go1.8.7 env GOROOT)"

Using goX.Y.Z as go

Often in a project we have some kind of build scripts of Makefiles which will call go instead of go1.8.7 to build our Go binary. Therefore it would be very convenient if we can use the executable go1.8.7 as go for a specific directory/project. This is where direnv comes into play.

direnv is an environment switcher for the shell. It knows how to hook into
bash, zsh, tcsh, fish shell and elvish to load or unload environment
variables depending on the current directory

For demostration purposes, we will create a new project in the GOPATH as following:

$ export GOPATH="$(go1.8.7 env GOPATH)"
$ mkdir -p "${GOPATH}/src/github.com/user/hello"
$ cd "${GOPATH}/src/github.com/user/hello"
$ cat >main.go <<EOL
package main

import "fmt"

func main() {
    fmt.Println("Hello, world.")
}
EOL

In order to enable direnv in our project directory, we need to setup the .envrc file. This can be done by doing

$ direnv edit .

inside the root directory of our project. The content of .envrc file should be:

export GOROOT="$(go1.8.7 env GOROOT)"
PATH_add "$(go1.8.7 env GOROOT)/bin"

In the first line, we point GOROOT to the version that we want to work with. Then we add the Go 1.8.7 compiler into PATH so that it will be found before the default one. Once the setup is done, running go version will give us the older version.

$ go version
go version go1.8.7 linux/amd64

We can then build the main.go using

$ go build
$ gdb ./hello
...
(gdb) p 'runtime.buildVersion'
$1 = 0x4a5208 "go1.8.7"

The above also shows how to check the which version of Go is used to build the hello binary as described in this post.

---

That's all for the demo. Hope you find this post useful. Personally I think that this approach has a good balance between simplicity and usability. One other thing that I often find useful in tools like pyenv is the pyenv install --list subcommand which shows the available versions that can be installed with pyenv. Of course the approach above does not have this feature. One hack we can use to list all available versions on terminal is by using the pup command with curl:

$ curl -s https://godoc.org/golang.org/dl | pup 'body > div.container > table > tbody > tr > td:nth-child(1) > a text{}'

go1.10
go1.10.1
go1.10.2
go1.10.3
go1.10.4
...

It's not pretty but it does the trick 💪.

Found a typo?

Thank you for reading! Found a typo? See something that could be improved or anything else that should be updated on this blog post? Thanks to this project, you can easily create a pull request on https://github.com/shihanng/dev.to to propose a fix!