StreamWrapperExampleController.php

<?php

namespace Drupal\stream_wrapper_example\Controller;

use Drupal\Core\Controller\ControllerBase;

/**
 * Controller class for the Stream Wrapper Example.
 */
class StreamWrapperExampleController extends ControllerBase {
    
    /**
     * Description page for the example.
     */
    public function description() {
        $build = [
            'description' => [
                '#theme' => 'example_description',
            ],
        ];
        return $build;
    }

}