How to send notifications following recent Firestore updates using Firebase FCM and Ionic Native - ionic-framework

Question

I am trying to set up Cloud Messaging Functions using https://www.youtube.com/watch?v=SOOjamH1bAA&t=317s
The code for my question is at 7:35 of this video. The full doc is in the link accessible from the video.
I am struggling with the recent updates to Firestore (see https://firebase.google.com/docs/functions/beta-v1-diff#cloud-firestore ), especially for time 7:35 of the youtube video link above. following the updates I changed the .onCreate to:
exports.newSubscriberNotification = functions.firestore
.document('subscribers/{subscriberId}')
.onCreate((snap,context) => { //I notice no async event...
const data = snap.data();
The problem is: 'await' expression is only allowed within an async function. This makes sense as there is no longer an 'async event' due to the update.
const devices = await devicesRef.get(); //see time 8:25 of video above.
If I add an async even above, the problem becomes: Property 'error' does not exist on type '“” | Promise' on the line:
devices.forEach(result => {...}) //see time 8:35 of video above.
I have tried multiple solutions found online but I'm digging myself in a hole. I think the problem is I am not triggering the index.ts function file (according to console.log() ).
Please bear with me - I am relatively new to app development.
import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
import { Subject } from 'rxjs/Subject';
import { tap } from 'rxjs/operators';
admin.initializeApp();
console.log('before initializeApp');
exports.newSubscriberNotification = functions.firestore
.document('subscribers/{subscriberId}') //odd
.onCreate((snap,context) => {
const data = snap.data();
console.log('const data fired');
const userId = data.userId
const subscriber = data.subscriberId
console.log('gathered data')
// Notification content
const payload = {
notification: {
title: 'New Subscriber',
body: `${subscriber} is following your content!`,
}
}
// ref to the device collection for the user
const db = admin.firestore();
const devicesRef = db.collection('devices').where('userId', '==', userId);
// get the user's tokens and send notifications
console.log('before await');
const devices = await devicesRef.get();
console.log('async function');
console.log('before devices');
//devices();
console.log('after devices');
const tokens = [];
// send a notification to each device token
devices.forEach(result => {
const token = result.data().token;
tokens.push( token )
})
return admin.messaging().sendToDevice(tokens, payload)
});