Firestore FCM push notification Cloud Functions - Android

I was searching and I could not find the solution to my problem, I need an example of how to send FCM messages from a cloud function, but using FIRESTORE, and not database realtime ...

I need to make a query to a "user" document where I have the token to send the message ...

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.sendNotificaction = functions.firestore
    .document('messages/{messageID}')
    .onCreate((snap, context) => {

    const message = snap.data();
    const messageType = message.type;
    const userID = message.userID;

    console.log(messageType);
    console.log(userID);

    // I NEED TO QUERY MY "USER" DOC WITH "userID" TO GET THE TOKEN

        //let token = 'eHQMpJkde_o:APA91bGa5x1lWB7kbK92QgCGkpyMq4PuQJA83_tIMIfzRil1Poly7ZzVVLU2Cs0GCTs77jgQo1i6Nn3vpzrMl6X2Zw9tN3eQIuJSvXuqgNUTa2EJEkKAbmqiVb2MGGHhPTanITJ0lCgaFpQkJjgznfd-MO2pv9S2PQ';

        let payload = {
            notification: {
                title: 'Notificacion from firebase',
                body: 'Test',
                sound: 'default',
                badge: '1'
            }
        };
        return admin.messaging().sendToDevice(token, payload);
    //}
    });