Inject messenger

use Drupal\Core\Messenger\MessengerInterface;
/**
 * The messenger service.
 *
 * @var \Drupal\Core\Messenger\MessengerInterface
 */
protected $messenger;
/**
 * The form constructor.
 *
 * @param \Drupal\Core\Messenger\MessengerInterface $messenger
 *   The messenger service.
 */
public function __construct(MessengerInterface $messenger) {
 $this->messenger = $messenger;
}
 /**
 * {@inheritdoc}
 */
public static function create(ContainerInterface $container) {
 return new static(
   $container->get('messenger'),
 );
}