refactor: remove the ctx (#141)

Author: rickyes

app/controller/user.js

@@ -10,7 +10,7 @@ class UserController extends Controller {
   async index() {
     const { ctx, service, config } = this;
     const user_name = ctx.params.name;
-    const user = await ctx.service.user.getUserByLoginName(user_name);
+    const user = await service.user.getUserByLoginName(user_name);
     if (!user) {
       ctx.status = 404;
       ctx.message = '这个用户不存在。';