yii2-bootstrap/extensions/yii/gii/generators/module/templates/controller.php

<?php
/**
 * This is the template for generating a controller class within a module.
 *
 * @var yii\web\View $this
 * @var yii\gii\generators\module\Generator $generator
 */
echo "<?php\n";
?>

namespace <?= $generator->getControllerNamespace() ?>;

use yii\web\Controller;

class DefaultController extends Controller
{
	public function actionIndex()
	{
		return $this->render('index');
	}
}