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Gopls: Using Emacs

Installing gopls

To use gopls with Emacs, you must first install the gopls binary and ensure that the directory containing the resulting binary (either $(go env GOBIN) or $(go env GOPATH)/bin) is in your PATH.

Choosing an Emacs LSP client

To use gopls with Emacs, you will need to choose and install an Emacs LSP client package. Two popular client packages are LSP Mode and Eglot.

LSP Mode takes a batteries-included approach, with many integrations enabled “out of the box” and several additional behaviors provided by lsp-mode itself.

Eglot takes a minimally-intrusive approach, focusing on smooth integration with other established packages. It provides a few of its own eglot- commands but no additional keybindings by default.

Once you have selected which client you want to use, install it per the packages instructions: see Eglot 1-2-3 or LSP Mode Installation.

Common configuration

Both Eglot and LSP Mode can integrate with popular packages in the Emacs ecosystem:

  • The built-in xref package provides cross-references.
  • The built-in Flymake package provides an on-the-fly diagnostic overlay.
  • Company mode displays code completion candidates (with a richer UI than the built-in completion-at-point).

Eglot provides documentation using the built-in ElDoc minor mode, while LSP Mode by default provides documentation using its own lsp-ui mode.

Eglot by default locates the project root using the [project] package. In LSP Mode, this behavior can be configured using the lsp-auto-guess-root setting.

Configuring LSP Mode

Loading LSP Mode in .emacs

(require 'lsp-mode)
(add-hook 'go-mode-hook #'lsp-deferred)

;; Set up before-save hooks to format buffer and add/delete imports.
;; Make sure you don't have other gofmt/goimports hooks enabled.
(defun lsp-go-install-save-hooks ()
  (add-hook 'before-save-hook #'lsp-format-buffer t t)
  (add-hook 'before-save-hook #'lsp-organize-imports t t))
(add-hook 'go-mode-hook #'lsp-go-install-save-hooks)

Configuring gopls via LSP Mode

See settings for information about available gopls settings.

Stable gopls settings have corresponding configuration variables in lsp-mode. For example, (setq lsp-gopls-use-placeholders nil) will disable placeholders in completion snippets. See lsp-go for a list of available variables.

Experimental settings can be configured via lsp-register-custom-settings:

(lsp-register-custom-settings
 '(("gopls.completeUnimported" t t)
   ("gopls.staticcheck" t t)))

Note that after changing settings you must restart gopls using e.g. M-x lsp-restart-workspace.

Configuring Eglot

Configuring project for Go modules in .emacs

Eglot uses the built-in project package to identify the LSP workspace for a newly-opened buffer. The project package does not natively know about GOPATH or Go modules. Fortunately, you can give it a custom hook to tell it to look for the nearest parent go.mod file (that is, the root of the Go module) as the project root.

(require 'project)

(defun project-find-go-module (dir)
  (when-let ((root (locate-dominating-file dir "go.mod")))
    (cons 'go-module root)))

(cl-defmethod project-root ((project (head go-module)))
  (cdr project))

(add-hook 'project-find-functions #'project-find-go-module)

Loading Eglot in .emacs

;; Optional: load other packages before eglot to enable eglot integrations.
(require 'company)
(require 'yasnippet)

(require 'go-mode)
(require 'eglot)
(add-hook 'go-mode-hook 'eglot-ensure)

;; Optional: install eglot-format-buffer as a save hook.
;; The depth of -10 places this before eglot's willSave notification,
;; so that that notification reports the actual contents that will be saved.
(defun eglot-format-buffer-before-save ()
  (add-hook 'before-save-hook #'eglot-format-buffer -10 t))
(add-hook 'go-mode-hook #'eglot-format-buffer-before-save)

Use M-x eglot-upgrade-eglot to upgrade to the latest version of Eglot.

Configuring gopls via Eglot

See settings for information about available gopls settings.

LSP server settings are controlled by the eglot-workspace-configuration variable, which can be set either globally in .emacs or in a .dir-locals.el file in the project root.

.emacs:

(setq-default eglot-workspace-configuration
    '((:gopls .
        ((staticcheck . t)
         (matcher . "CaseSensitive")))))

.dir-locals.el:

((nil (eglot-workspace-configuration . ((gopls . ((staticcheck . t)
						  (matcher . "CaseSensitive")))))))

Organizing imports with Eglot

gopls provides the import-organizing functionality of goimports as an LSP code action, which you can invoke as needed by running M-x eglot-code-actions (or a key of your choice bound to the eglot-code-actions function) and selecting Organize Imports at the prompt.

To automatically organize imports before saving, add a hook:

(add-hook 'before-save-hook
    (lambda ()
        (call-interactively 'eglot-code-action-organize-imports))
    nil t)

Troubleshooting

Common errors:

  • When prompted by Emacs for your project folder, if you are using modules you must select the module's root folder (i.e. the directory with the "go.mod"). If you are using GOPATH, select your $GOPATH as your folder.
  • Emacs must have your environment set properly (PATH, GOPATH, etc). You can run M-x getenv <RET> PATH <RET> to see if your PATH is set in Emacs. If not, you can try starting Emacs from your terminal, using [this package][exec-path-from-shell], or moving your shell config from .bashrc into .profile and logging out and back in.
  • Make sure only one LSP client mode is installed. (For example, if using lsp-mode, ensure that you are not also enabling eglot.)
  • Look for errors in the *lsp-log* buffer or run M-x eglot-events-buffer.
  • Ask for help in the #emacs channel on the Gophers slack.