title: send flutter firebase cloud messaging when app is completely shut down
body: <p>I am following the FCM from <a href="https://pub.dev/packages/firebase_messaging" rel="nofollow noreferrer">https://pub.dev/packages/firebase_messaging</a>
  and if I am in app or I press home button and do not close app completely , the messages will be sent and every thing is good , but if I close the app completely , the messages will not be send .</p>
  
  <p>what do I should doing ?</p>