title: Laravel/Lumen event listener does not listen
body: <p>I have a Lumen controller class that fires an event when a user is created. I am using an event dispatcher. The event gets fired as it should, but the listener does not handle the event.
  I am sure I have followed every step of the Lumen documentation.</p>
  
  <pre><code>// UserController.php
  class UserController extends ApiController
  {
       protected $event = null;
  
       public function __construct(Dispatcher $event)
       {
           $this-&gt;event = $event;
       }
  
      /**
       * Store a newly created resource in storage.
       *
       * @param Request $request
       * @return Response
       */
      public function store(Request $request)
      {
           $this-&gt;acceptContentType($request, 'json');
  
           $this-&gt;input = $request-&gt;json()-&gt;all();
           $this-&gt;withEncryptedParameters();
  
           $this-&gt;validateParameterNames(array_keys($this-&gt;validationRules));
           $this-&gt;validateParameterContent($this-&gt;validationRules);
  
           $roles = $this-&gt;getRelationInput('roles');
  
           $user = User::create($this-&gt;input);
           $this-&gt;addRelation($user, $roles, Role::class, 'roles');
  
           $this-&gt;event-&gt;fire(new UserCreated($user));
  
           return $this-&gt;respondCreated($user-&gt;id);
       }
  }
  </code></pre>
  
  <p>So I basically want to store a user into the database and fire an event when that happens.</p>
  
  <pre><code>// UserCreated.php
  class UserCreated extends Event
  {
      public $user;
  
      public function __construct(User $user)
      {
          $this-&gt;user = $user;
      }
  }
  </code></pre>
  
  <p>The event is fired correctly, so if I put an "echo" or a "var_dump" into the event's constructor, I can see that it works. If I so the same for the listener, it does not react.</p>
  
  <pre><code>// UserCreatedEmail.php
  class UserCreatedEmail extends Listener
  {
      public function handle(UserCreated $event)
      {
          echo 'Hello?';
      }
  }
  </code></pre>
  
  <p>I have registered it in the EventServiceProvider.</p>
  
  <pre><code>// EventServiceProvider.php
  class EventServiceProvider extends ServiceProvider
  {
      /**
       * The event listener mappings for the application.
       *
       * @var array
       */
      protected $listen = [
          UserCreated::class =&gt; [
              UserCreatedEmail::class
          ]
      ];
  }
  </code></pre>
  
  <p>And uncommented it in the bootstrap area.</p>
  
  <pre><code>// bootstrap/app.php    
  $app-&gt;register(WISSIT\UserService\Providers\EventServiceProvider::class);
  </code></pre>
  
  <p>I have absolutely no idea why is doesn't work. I could use "$event->listen" but then it would also listen when I use testing. According to the Lumen documentation, it should also work without that.</p>
  
  <p>And yes, the namespaces are set correctly. And no, I do not want to use Facades.</p>