How to pass a url(data) or message to app using FCM in flutter?

How to pass a URL throw FCM in a flutter, I already implemented an FCM and received notification, but can't pass data, how to implement that?

A URL as data message from firebase to app using FCM

FirebaseMessaging _firebaseMessaging = FirebaseMessaging();
void initState() {

void firebaseCloudMessaging_Listeners() {
 if (Platform.isIOS) iOS_Permission();
  Navigator.push(context, MaterialPageRoute(
      builder: (context) => PageStack(pages: ContactUs(test: token,), title: "Contact Us", back: true,)));

  onMessage: (Map<String, dynamic> message) async {
    print('on message $message');
  onResume: (Map<String, dynamic> message) async {
    print('on resume $message');
  onLaunch: (Map<String, dynamic> message) async {
    print('on launch $message');

void iOS_Permission() {
    IosNotificationSettings(sound: true, badge: true, alert: true)
    .listen((IosNotificationSettings settings)
  print("Settings registered: $settings");