import { Firebase } from '@awesome-cordova-plugins/firebase/ngx';
constructor(private firebase: Firebase) { }
...
this.firebase.getToken()
  .then(token => console.log(`The token is ${token}`)) 
  .catch(error => console.error('Error getting token', error));
this.firebase.onNotificationOpen()
   .subscribe(data => console.log(`User opened a notification ${data}`));
this.firebase.onTokenRefresh()
  .subscribe((token: string) => console.log(`Got a new token ${token}`));