How to use the web-push.setVapidDetails function in web-push

// Use the web-push library to hide the implementation details of the communication
// between the application server and the push service.
// For details, see https://tools.ietf.org/html/draft-ietf-webpush-protocol and
// https://tools.ietf.org/html/draft-ietf-webpush-encryption.
const webPush = require('web-push');

if (!process.env.VAPID_PUBLIC_KEY || !process.env.VAPID_PRIVATE_KEY) {
  console.log("You must set the VAPID_PUBLIC_KEY and VAPID_PRIVATE_KEY "+
    "environment variables. You can use the following ones:");
  console.log(webPush.generateVAPIDKeys());
  return;
}
// Set the keys used for encrypting the push messages.
webPush.setVapidDetails(
  'https://serviceworke.rs/',
  process.env.VAPID_PUBLIC_KEY,
  process.env.VAPID_PRIVATE_KEY
);

const payloads = {};

module.exports = function(app, route) {
  app.get(route + 'vapidPublicKey', function(req, res) {
    res.send(process.env.VAPID_PUBLIC_KEY);
  });

  app.post(route + 'register', function(req, res) {
    // A real world application would store the subscription info.
    res.sendStatus(201);
  });

})
}));
app.use(passport.initialize());
app.use(passport.session()); // persistent login sessions
app.use(flash()); // use connect-flash for flash messages stored in session
app.use(function (req, res, next) {
  res.locals.sessionFlash = req.session.sessionFlash;
  delete req.session.sessionFlash;
  next();
});

//set up webpush to send push notifications for the notifier
webpush = require('web-push');
if (!auth.vapidPrivateKey || !auth.vapidPublicKey) {
  vapidKeys = webpush.generateVAPIDKeys();
  webpush.setVapidDetails(
    'mailto:support@sweet.sh',
    vapidKeys.publicKey,
    vapidKeys.privateKey
  );
} else {
  webpush.setVapidDetails(
    'mailto:support@sweet.sh',
    auth.vapidPublicKey,
    auth.vapidPrivateKey
  );
}

//kill the process when the sigint code is recieved, generally generated by pressing ctrl-c in the console
app.on('SIGINT', function () {
  db.stop(function (err) {
    process.exit(err ? 1 : 0);

var express = require('express');
var cors = require('cors');
var app = express();
app.use(cors());
app.options('*', cors());

var bodyParser = require('body-parser');
var jsonParser = bodyParser.json();
var PORT = process.env.PORT || 8090;
var webPush = require('web-push');

// The GCM API key is AIzaSyDNlm9R_w_0FDGjSM1fzyx5I5JnJBXACqU
webPush.setVapidDetails(
  'mailto:salnikov@gmail.com',
  'BHe82datFpiOOT0k3D4pieGt1GU-xx8brPjBj0b22gvmwl-HLD1vBOP1AxlDKtwYUQiS9S-SDVGYe_TdZrYJLw8',
  's-zBxZ1Kl_Y1Ac8_uBjwIjtLtG6qlJKOX5trtbanAhc'
);

app.use(express.static(__dirname));

app.use(bodyParser.json());

app.use("/push", function(req, res, next) {
  //console.log(res.body);
  if (req.body.action === 'subscribe') {
    var endpoint = req.body.subscription;

    console.log(req);

let privateKey = process.env.VAPID_PRIVATE_KEY
let publicKey = process.env.VAPID_PUBLIC_KEY
const linkingNotifyEndpoint = process.env.LINKING_NOTIFY_ENDPOINT
const linkingNotifyToken = process.env.LINKING_NOTIFY_TOKEN
const dappOfferUrl = process.env.DAPP_OFFER_URL

if (!privateKey || !publicKey) {
  console.log(
    'Warning: VAPID public or private key not defined, generating one'
  )
  const vapidKeys = webpush.generateVAPIDKeys()
  publicKey = vapidKeys.publicKey
  privateKey = vapidKeys.privateKey
}

webpush.setVapidDetails(`mailto:${emailAddress}`, publicKey, privateKey)

// should be tightened up for security
app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*')
  res.header(
    'Access-Control-Allow-Headers',
    'Origin, X-Requested-With, Content-Type, Accept'
  )

  next()
})

// limit request to one per minute
const rateLimiterOptions = {
  points: 1,
  duration: 60

* Not necessary to be JavaScript server, choose your favorite language ;)
 */

const http  = require("http"),
      https = require("https"),
      fs    = require("fs");

// A library for handling VAPID and encrypting of Web-Push-Protocol.
// See https://github.com/web-push-libs/web-push for more information.
const webpush = require("web-push");

// "./application-server-keys.json" should be automatically generated by "postinstall"
const keys = require("./application-server-keys.json");

// Initialize library with **YOUR** project keys and settings.
webpush.setVapidDetails(
  process.env.SENDER_EMAIL || "mailto:otiai10@gmail.com",
  keys.publicKey,
  keys.privateKey
);

const subscribers = [
  // Here would be any subscribers endpoints,
  // therefore this is gonna be a list of, so called, "target list".
  // You should sotre this list to your database to make it persistent.
];

const controllers = {
  /**
   * ============================
   * == THIS IS NOT IMPORTANT! ==
   * ============================

const sendPushNotification = (root, args, context) => {
  const { user } = context;

  Users.utils.checkLoggedInAndVerified(user);

  // Set web-push keys
  webPush.setGCMAPIKey(gcmPrivateKey);
  webPush.setVapidDetails(vapidSubject, vapidPublicKey, vapidPrivateKey);

  const payload = JSON.stringify({
    title: 'Welcome',
    body: 'Thank you for enabling push notifications',
    icon: '/android-chrome-192x192.png',
  });

  const options = {
    TTL: 60, // time to live in seconds
  };

  // Gather all subscriptions from all subscribed users
  const selector = { subscriptions: { $exists: true, $ne: [] } };
  const projection = { fields: { _id: true, subscriptions: true } };
  const users = Users.collection.find(selector, projection).fetch();
  const subscriptions = flatten(map(users, 'subscriptions'));

function init(cb) {
    web_push_1.setVapidDetails('mailto:bryan@nebri.us', util_1.getEnvironmentVariable('PUSH_PUBLIC_KEY'), util_1.getEnvironmentVariable('PUSH_PRIVATE_KEY'));
    console.log('Notifications initialied');
    setImmediate(cb);
}
exports.init = init;

public setup(httpServer: HttpServer): void {
        webpush.setVapidDetails(
            'mailto:example@yourdomain.org',
            this.vapidKeys.public,
            this.vapidKeys.private
        );
        httpServer.post('/push/register', this._register.bind(this));
        httpServer.post('/push/notifyAll', this._notifyAll.bind(this));
        httpServer.get('/push/clear', this._clearSubscriptions.bind(this));
    }

.then(function(){
            webpush.setVapidDetails('mailto:monkey030210@gmail.com',
             vapidKeys.publicKey,
             vapidKeys.privateKey
             );
             return admin.database().ref('subscriptions').once('value');
        })
        .then(function(subs){