feat: add "go mod" support

lua/gopher/gomod.lua

@@ -0,0 +1,19 @@
+local Job = require "plenary.job"
+
+return function(...)
+  local args = { ... }
+  local cmd_args = vim.list_extend({ "mod" }, args)
+
+  Job
+    :new({
+      command = "go",
+      args = cmd_args,
+      on_exit = function(_, retval)
+        if retval ~= 0 then
+          print("command exited with code " .. retval)
+          return
+        end
+      end,
+    })
+    :sync()
+end

lua/gopher/init.lua

@@ -4,5 +4,6 @@ local gopher = {}
 gopher.install_deps = require("gopher.installer").install_all
 gopher.tags_add = tags.add
 gopher.tags_rm = tags.remove
+gopher.mod = require "gopher.gomod"
 
 return gopher