add golang configuration

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,
+}