set up gopls and basic go formatting

Author: jdhao

after/ftplugin/go.lua

@@ -0,0 +1,5 @@
+-- gofumpt adds more rule to gofmt, and is compatible with gofmt,
+-- so also https://github.com/mvdan/gofumpt
+vim.keymap.set("n", "<Space>f", function()
+  vim.cmd([[silent !gofumpt -w %]])
+end, { buffer = true, silent = true })

after/lsp/gopls.lua

@@ -0,0 +1,14 @@
+-- settings for gopls can be found in https://go.dev/gopls/settings
+---@type vim.lsp.Config
+return {
+  settings = {
+    gopls = {
+      usePlaceholders = true,
+      analyses = {
+        unusedparams = true,
+      },
+      staticcheck = true,
+      gofumpt = true,
+    },
+  },
+}