🚙 Like pyenv and rbenv, but for Go.
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Signed-off-by: Anton Antonov <anton.synd.antonov@gmail.com>
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README.md

Go Version Management: goenv

goenv aims to be as simple as possible and follow the already estabilished successful version management model of pyenv and rbenv.

This project was cloned from pyenv and modified for Go.

asciicast

goenv does...

  • Let you change the global Go version on a per-user basis.
  • Provide support for per-project Go versions.
  • Allow you to override the Go version with an environment variable.
  • Search commands from multiple versions of Go at a time.

goenv compared to others:


Table of Contents


How It Works

At a high level, goenv intercepts Go commands using shim executables injected into your PATH, determines which Go version has been specified by your application, and passes your commands along to the correct Go installation.

Understanding PATH

When you run all the variety of Go commands using go, your operating system searches through a list of directories to find an executable file with that name. This list of directories lives in an environment variable called PATH, with each directory in the list separated by a colon:

/usr/local/bin:/usr/bin:/bin

Directories in PATH are searched from left to right, so a matching executable in a directory at the beginning of the list takes precedence over another one at the end. In this example, the /usr/local/bin directory will be searched first, then /usr/bin, then /bin.

Understanding Shims

goenv works by inserting a directory of shims at the front of your PATH:

~/.goenv/shims:/usr/local/bin:/usr/bin:/bin

Through a process called rehashing, goenv maintains shims in that directory to match every go command across every installed version of Go.

Shims are lightweight executables that simply pass your command along to goenv. So with goenv installed, when you run go your operating system will do the following:

  • Search your PATH for an executable file named go
  • Find the goenv shim named go at the beginning of your PATH
  • Run the shim named go, which in turn passes the command along to goenv

Choosing the Go Version

When you execute a shim, goenv determines which Go version to use by reading it from the following sources, in this order:

  1. The GOENV_VERSION environment variable (if specified). You can use the goenv shell command to set this environment variable in your current shell session.

  2. The application-specific .go-version file in the current directory (if present). You can modify the current directory's .go-version file with the goenv local command.

  3. The first .go-version file found (if any) by searching each parent directory, until reaching the root of your filesystem.

  4. The global ~/.goenv/version file. You can modify this file using the goenv global command. If the global version file is not present, goenv assumes you want to use the "system" Go. (In other words, whatever version would run if goenv isn't present in PATH.)

NOTE: You can activate multiple versions at the same time, including multiple versions of Go simultaneously or per project.

Locating the Go Installation

Once goenv has determined which version of Go your application has specified, it passes the command along to the corresponding Go installation.

Each Go version is installed into its own directory under ~/.goenv/versions.

For example, you might have these versions installed:

  • ~/.goenv/versions/1.6.1/
  • ~/.goenv/versions/1.6.2/

As far as goenv is concerned, version names are simply the directories in ~/.goenv/versions.

Installation

If you're on Mac OS X, consider installing with Homebrew.

Basic GitHub Checkout

This will get you going with the latest version of goenv and make it easy to fork and contribute any changes back upstream.

  1. Check out goenv where you want it installed. A good place to choose is $HOME/.goenv (but you can install it somewhere else).

     $ git clone https://github.com/syndbg/goenv.git ~/.goenv
    
  2. Define environment variable GOENV_ROOT to point to the path where goenv repo is cloned and add $GOENV_ROOT/bin to your $PATH for access to the goenv command-line utility.

     $ echo 'export GOENV_ROOT="$HOME/.goenv"' >> ~/.bash_profile
     $ echo 'export PATH="$GOENV_ROOT/bin:$PATH"' >> ~/.bash_profile
    

    Zsh note: Modify your ~/.zshenv file instead of ~/.bash_profile. Ubuntu note: Modify your ~/.bashrc file instead of ~/.bash_profile.

  3. Add goenv init to your shell to enable shims and autocompletion. Please make sure eval "$(goenv init -)" is placed toward the end of the shell configuration file since it manipulates PATH during the initialization.

     $ echo 'eval "$(goenv init -)"' >> ~/.bash_profile
    

    Zsh note: Modify your ~/.zshenv file instead of ~/.bash_profile. Ubuntu note: Modify your ~/.bashrc file instead of ~/.bash_profile.

    General warning: There are some systems where the BASH_ENV variable is configured to point to .bashrc. On such systems you should almost certainly put the abovementioned line eval "$(goenv init -) into .bash_profile, and not into .bashrc. Otherwise you may observe strange behaviour, such as goenv getting into an infinite loop. See pyenv's issue #264 for details.

  4. Restart your shell so the path changes take effect. You can now begin using goenv.

     $ exec $SHELL
    
  5. Install Go versions into $GOENV_ROOT/versions. For example, to download and install Go 1.6.2, run:

     $ goenv install 1.6.2
    

    NOTE: It downloads and places the prebuilt Go binaries provided by Google.

Upgrading

If you've installed goenv using the instructions above, you can upgrade your installation at any time using git.

To upgrade to the latest development version of goenv, use git pull:

$ cd ~/.goenv
$ git pull

To upgrade to a specific release of goenv, check out the corresponding tag:

$ cd ~/.goenv
$ git fetch
$ git tag
v20160417
$ git checkout v20160417

Uninstalling goenv

The simplicity of goenv makes it easy to temporarily disable it, or uninstall from the system.

  1. To disable goenv managing your Go versions, simply remove the goenv init line from your shell startup configuration. This will remove goenv shims directory from PATH, and future invocations like goenv will execute the system Go version, as before goenv.

goenv will still be accessible on the command line, but your Go apps won't be affected by version switching.

  1. To completely uninstall goenv, perform step (1) and then remove its root directory. This will delete all Go versions that were installed under `goenv root`/versions/ directory:

     rm -rf `goenv root`
    

    If you've installed goenv using a package manager, as a final step perform the goenv package removal. For instance, for Homebrew:

     brew uninstall goenv
    

Command Reference

Homebrew on Mac OS X

You can also install goenv using the Homebrew package manager for Mac OS X.

$ brew update
$ brew install goenv

To upgrade goenv in the future, use upgrade instead of install.

After installation, you'll need to add eval "$(goenv init -)" to your profile (as stated in the caveats displayed by Homebrew — to display them again, use brew info goenv). You only need to add that to your profile once.

Then follow the rest of the post-installation steps under "Basic GitHub Checkout" above, starting with #4 ("restart your shell so the path changes take effect").

Advanced Configuration

Skip this section unless you must know what every line in your shell profile is doing.

goenv init is the only command that crosses the line of loading extra commands into your shell. Coming from rvm, some of you might be opposed to this idea. Here's what goenv init actually does:

  1. Sets up your shims path. This is the only requirement for goenv to function properly. You can do this by hand by prepending ~/.goenv/shims to your $PATH.

  2. Installs autocompletion. This is entirely optional but pretty useful. Sourcing ~/.goenv/completions/goenv.bash will set that up. There is also a ~/.goenv/completions/goenv.zsh for Zsh users.

  3. Rehashes shims. From time to time you'll need to rebuild your shim files. Doing this on init makes sure everything is up to date. You can always run goenv rehash manually.

  4. Installs the sh dispatcher. This bit is also optional, but allows goenv and plugins to change variables in your current shell, making commands like goenv shell possible. The sh dispatcher doesn't do anything crazy like override cd or hack your shell prompt, but if for some reason you need goenv to be a real script rather than a shell function, you can safely skip it.

To see exactly what happens under the hood for yourself, run goenv init -.

Uninstalling Go Versions

As time goes on, you will accumulate Go versions in your ~/.goenv/versions directory.

To remove old Go versions, goenv uninstall command to automate the removal process.

Alternatively, simply rm -rf the directory of the version you want to remove. You can find the directory of a particular Go version with the goenv prefix command, e.g. goenv prefix 1.6.2.


Command Reference

See COMMANDS.md.


Environment variables

You can affect how goenv operates with the following settings:

name default description
GOENV_VERSION Specifies the Go version to be used.
Also see goenv shell
GOENV_ROOT ~/.goenv Defines the directory under which Go versions and shims reside.
Also see goenv root
GOENV_DEBUG Outputs debug information.
Also as: goenv --debug <subcommand>
GOENV_HOOK_PATH Colon-separated list of paths searched for goenv hooks.
GOENV_DIR $PWD Directory to start searching for .go-version files.

Development

The goenv source code is hosted on GitHub. It's clean, modular, and easy to understand, even if you're not a shell hacker. (I hope)

Tests are executed using Bats:

$ bats test
$ bats/test/<file>.bats

Please feel free to submit pull requests and file bugs on the issue tracker.