I'm trying to create modules in Codeigniter 4 to work with HMVC. I tried following this user guide <https://codeigniter4.github.io/userguide/general/modules.html>, but cannot get it working.

I created a 'modules' folder, alongside the app, public, etc. folders. 

Added to `app/config/autoload.php` 

```
'Modules' => ROOTPATH.'modules'

```

Inside the modules folder, I created a 'Proef' folder, containing a Controllers folder and 'Proef.php' file.

The file contains the following;

```php
    namespace App\Modules\Proef\Controllers;
    class Proef extends \CodeIgniter\Controller
    {
      public function index() {
        echo 'hello!';
      }
    }

```

In the `app/config.routes.php` file I added

```php
    $routes->group('proef', ['namespace' => 'Modules\Proef\Controllers'], function($routes)
    {
        $routes->get('/', 'Proef::index');
    });

```

Yet, the following error persists:
Controller or its method is not found: `\Modules\Proef\Controllers\Proef::index`

What am I missing?