gopls (go lsp-mode) config for emacs with useful optional packages.

gopls-config.el

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Pre gopls/lsp-mode/go-mode setup
;;; This section installs use-package from melpa if it isn't
;;; already installed. You can skip this if you already have use-package

;; enable melpa if it isn't enabled
(require 'package)
(when (not (assoc "melpa" package-archives))
  (setq package-archives (append '(("melpa" . "https://melpa.org/packages/")) package-archives)))
(package-initialize)

;; refresh package list if it is not already available
(when (not package-archive-contents) (package-refresh-contents))

;; install use-package if it isn't already installed
(when (not (package-installed-p 'use-package))
  (package-install 'use-package))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Install and configure pacakges

;; optional, provides snippets for method signature completion
(use-package yasnippet
  :ensure t)

(use-package lsp-mode
  :ensure t
  ;; uncomment to enable gopls http debug server
  ;; :custom (lsp-gopls-server-args '("-debug" "127.0.0.1:0"))
  :commands (lsp lsp-deferred)
  :config (progn
            ;; use flycheck, not flymake
            (setq lsp-prefer-flymake nil)))

;; optional - provides fancy overlay information
(use-package lsp-ui
  :ensure t
  :commands lsp-ui-mode
  :config (progn
            ;; disable inline documentation
            (setq lsp-ui-sideline-enable nil)
            ;; disable showing docs on hover at the top of the window
            (setq lsp-ui-doc-enable nil))
  )

(use-package company
  :ensure t
  :config (progn
            ;; don't add any dely before trying to complete thing being typed
            ;; the call/response to gopls is asynchronous so this should have little
            ;; to no affect on edit latency
            (setq company-idle-delay 0)
            ;; start completing after a single character instead of 3
            (setq company-minimum-prefix-length 1)
            ;; align fields in completions
            (setq company-tooltip-align-annotations t)
            )
  )

;; optional package to get the error squiggles as you edit
(use-package flycheck
  :ensure t)

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

(use-package go-mode
  :ensure t
  :bind (
         ;; If you want to switch existing go-mode bindings to use lsp-mode/gopls instead
         ;; uncomment the following lines
         ;; ("C-c C-j" . lsp-find-definition)
         ;; ("C-c C-d" . lsp-describe-thing-at-point)
         )
  :hook ((go-mode . lsp-deferred)
         (before-save . lsp-format-buffer)
         (before-save . lsp-organize-imports)))

(provide 'gopls-config)

I think you have to set (setq lsp-prefer-flymake nil) to make it actually use flycheck.

I removed the set-library-path piece of the config as that is now integrated into lsp-mode.

This config is now out of date. You probably want to look at the example in the gopls docs instead: https://github.com/golang/tools/blob/master/gopls/doc/emacs.md