getToken function with Firebase 8

getFirebaseToken.ts

import firebase from 'firebase/app';
import 'firebase/messaging';
import { getConfig, getPublicKey, registerServiceWorker } from './firebase';

export async function getFirebaseToken() {
  firebase.initializeApp(getConfig());
  return firebase.messaging().getToken({
    vapidKey: getPublicKey(),
    serviceWorkerRegistration: await registerServiceWorker(),
  });
}