gopls/doc/advanced.md

# Advanced topics

This documentation is for advanced `gopls` users, who may want to test
unreleased versions or try out special features.

## Installing unreleased versions

To get a specific version of `gopls` (for example, to test a prerelease
version), run:

```sh
GO111MODULE=on go install golang.org/x/tools/gopls@vX.Y.Z
```

Where `vX.Y.Z` is the desired version.

### Unstable versions

To update `gopls` to the latest **unstable** version, use:

```sh
# Create an empty go.mod file, only for tracking requirements.
cd $(mktemp -d)
go mod init gopls-unstable

# Use 'go get' to add requirements and to ensure they work together.
go get golang.org/x/tools/gopls@master golang.org/x/tools@master

# For go1.17 or older, the above `go get` command will build and
# install `gopls`. For go1.18+ or tip, run the following command to install
# using selected versions in go.mod.
go install golang.org/x/tools/gopls
```

## Working on the Go source distribution

If you are working on the [Go project] itself, the `go` command that `gopls`
invokes will have to correspond to the version of the source you are working
on. That is, if you have checked out the Go project to `$HOME/go`, your `go`
command should be the `$HOME/go/bin/go` executable that you built with
`make.bash` or equivalent.

You can achieve this by adding the right version of `go` to your `PATH`
(`export PATH=$HOME/go/bin:$PATH` on Unix systems) or by configuring your
editor.

## Working with generic code

Gopls has beta support for editing generic Go code, as defined by the type
parameters proposal ([golang/go#43651](https://golang.org/issues/43651)) and
type set addendum ([golang/go#45346](https://golang.org/issues/45346)).

To enable this support, you need to build gopls with a version of Go that
supports generics. The easiest way to do this is by installing Go 1.18 Beta
1 as described at
[Tutorial: Getting started with generics#prerequisites](https://go.dev/doc/tutorial/generics),
and then using this Go version to build gopls:

```
$ go1.18beta1 install golang.org/x/tools/gopls@latest
```

When using the Go 1.18, it is strongly recommended that you install the latest
version of `gopls`, or the latest **unstable** version as
[described above](#installing-unreleased-versions).

The `gopls` built with these instructions understands generic code. To actually
run the generic code you develop, you must also use the beta version of the Go
compiler. For example:

```
$ go1.18beta1 run .
```

[Go project]: https://go.googlesource.com/go