title: Fresh laravel lumen cannot find controller reside under subfolder of controllers
body: <p>Fresh laravel <code>lumen 5.8</code> installed but controller name cannot be found in route</p>
  
  <p>I created <code>UserController</code> in <code>App\Http\Controllers\User</code></p>
  
  <p>User Controller Content:</p>
  
  <pre class="lang-php prettyprint-override"><code>namespace App\Http\Controllers;
  
  class UserController extends Controller {
     public function index() {
        return 'User list';
     }
  }
  </code></pre>
  
  <p>Loaded in route:</p>
  
  <pre class="lang-php prettyprint-override"><code>$router-&gt;get('/user', 'User\UserController@index')
  </code></pre>
  
  <p>Error:</p>
  
  <blockquote>
    <p>Class App\Http\Controllers\User\UserController does not exist</p>
  </blockquote>
  
  <p>I also tried with absolute namespace <code>App\Http\Controllers\User\UserController@index</code> but it still doesn't work.</p>
  
  <p>It works if I don't put <code>UserController</code> in User folder</p>