add golang configuration

init.lua

@@ -587,7 +587,17 @@ require('mason-lspconfig').setup()
 --  define the property 'filetypes' to the map in question.
 local servers = {
   -- clangd = {},
-  -- gopls = {},
+  gopls = {
+    gopls = {
+      completeUnimported = true,
+      usePlaceholders = true,
+      analyses = {
+        unusedparams = true,
+        showdown = true,
+        unusedvariable = true,
+      },
+    },
+  },
   -- pyright = {},
   -- rust_analyzer = {},
   -- tsserver = {},

lua/custom/plugins/README.md

@@ -0,0 +1,10 @@
+### NULL-LS
+
+`goland`:
+
+```shell
+go install github.com/incu6us/goimports-reviser/v3@latest
+go install mvdan.cc/gofumpt@latest
+go install github.com/segmentio/golines@latest
+```
+

lua/custom/plugins/gopher.lua

@@ -0,0 +1,12 @@
+return {
+	'olexsmir/gopher.nvim',
+	ft = 'go',
+	config = function(_, opts)
+		require('gopher').setup(opts)
+
+		vim.keymap.set("n",	"<leader>gsj", "<CMD>GoTagAdd json<CR>", { desc = '[G]o add [S]truct [J]SON' })
+	end,
+	build = function()
+		vim.cmd [[silent! GoInstallDeps]]
+	end,
+}

lua/custom/plugins/null_ls.lua

@@ -0,0 +1,31 @@
+return {
+	'jose-elias-alvarez/null-ls.nvim',
+	ft = 'go',
+	config = function()
+		local null_ls = require('null-ls')
+		local augroup = vim.api.nvim_create_augroup('LspFormatting', {})
+
+		null_ls.setup {
+			sources = {
+				null_ls.builtins.formatting.goimports_reviser,
+				null_ls.builtins.formatting.gofumpt,
+				null_ls.builtins.formatting.golines,
+			},
+			on_attach = function(client, bufnr)
+				if client.supports_method('textDocument/formatting') then
+					vim.api.nvim_clear_autocmds({
+						group = augroup,
+						buffer = bufnr,
+					})
+					vim.api.nvim_create_autocmd("BufWritePre", {
+						group = augroup,
+						buffer = bufnr,
+						callback = function()
+							vim.lsp.buf.format({ bufnr = bufnr })
+						end,
+					})
+				end
+			end
+		}
+	end,
+}