modules/custom/d_p_subscribe_file/src/Controller/DownloadFile.php
private function goHomeWithMessage($message) {
    drupal_set_message($message);
    $url = Url::fromRoute('<front>');
    $response = new RedirectResponse($url->toString());
    $response->send();
  }
private function goHomeWithMessage($message) {
    drupal_set_message($message);
    $url = Url::fromRoute('<front>');
    $response = new RedirectResponse($url->toString());
    $response->send();
  }
Redirect to home page and show drupal message
@param $message