under maintenance

Problem: i have multiple routes files
I have created app with multiple modules, therefore each module has it's own routes file

I use filter for maintenance, but novadays we must echo the response in filter's before() method

PHP Code:

// Filter
public function before(RequestInterface $request, $arguments = null)
{
      if (!empty(getenv('maintenance'))) {
          echo FrontendMaintenanceController::maintenance();
          exit();
      }
}

// FrontendMaintenanceController
public static function maintenance()
{
    $maintenance = getenv('maintenance');

    if (empty((string) $maintenance)) {
        return redirect()->route('frontend-homepage');
    }

    return view(service('settings')->get('FrontendSettings.theme_path').'Base/maintenance', ['deadline' => $maintenance]);
}