Emacs

Use lsp-mode. gopls is built in now as a client, so no special config is necessary. You first must install gopls and put it somewhere in your PATH. Here is an example (assuming you are using use-package) to get you started:

(use-package lsp-mode
  :commands (lsp lsp-deferred))

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

;; optional - provides fancier overlays
(use-package lsp-ui
  :commands lsp-ui-mode)

;; if you use company-mode for completion (otherwise, complete-at-point works out of the box):
(use-package company-lsp
  :commands company-lsp)

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, or moving your shell config from .bashrc into .bashenv (or .zshenv).
• Make sure lsp-mode, lsp-ui and company-lsp are up-to-date, and make sure lsp-go is not installed.

To troubleshoot, look in the *lsp-log* buffer for errors.