gopls supports both Go module and GOPATH modes. However, it needs a defined scope in which language features like references, rename, and implementation should operate.
The following options are available for configuring this scope:
If you are working with a single module, you can open the module root (the directory containing the go.mod file), a subdirectory within the module, or a parent directory containing the module.
Note: If you open a parent directory containing a module, it must only contain that single module. Otherwise, you are working with multiple modules.
Gopls has several alternatives for working on multiple modules simultaneously, described below. Starting with Go 1.18, Go workspaces are the preferred solution.
Starting with Go 1.18, the go command has native support for multi-module workspaces, via go.work files. These files are recognized by gopls starting with gopls@v0.8.0.
The easiest way to work on multiple modules in Go 1.18 and later is therefore to create a go.work file containing the modules you wish to work on, and set your workspace root to the directory containing the go.work file.
For example, suppose this repo is checked out into the $WORK/tools directory. We can work on both golang.org/x/tools and golang.org/x/tools/gopls simultaneously by creating a go.work file:
cd $WORK go work init go work use tools tools/gopls
...followed by opening the $WORK directory in our editor.
With earlier versions of Go, gopls can simulate multi-module workspaces by creating a synthetic module requiring the the modules in the workspace root. See the design document for more information.
This feature is experimental, and will eventually be removed once go.work files are accepted by all supported Go versions.
You can enable this feature by configuring the experimentalWorkspaceModule setting.
If neither of the above solutions work, and your editor allows configuring the set of “workspace folders” used during your LSP session, you can still work on multiple modules by adding a workspace folder at each module root (the locations of go.mod files). This means that each module has its own scope, and features will not work across modules.
In VS Code, you can create a workspace folder by setting up a multi-root workspace. View the documentation for your editor plugin to learn how to configure a workspace folder in your editor.
When opening a directory within your GOPATH, the workspace scope will be just that directory.
Some users or companies may have projects that encompass one $GOPATH. If you open your entire $GOPATH or $GOPATH/src folder, the workspace scope will be your entire GOPATH. If your GOPATH is large, gopls to be very slow to start because it will try to find all of the Go files in the directory you have opened. It will then load all of the files it has found.
To work around this case, you can create a new $GOPATH that contains only the packages you want to work on.
If you have additional use cases that are not mentioned above, please file a new issue.