Express Passportjs Google + Custom Authentication - node.js

Question

I have an express application where I'm using passportjs for managing authentication.
At the moment I only want to support sign in with google in my application. I have implemented this properly and is working fine. Now, I want to restrict access to to the application to only those users who are registered with the application.
Registration is done by admin so there can only be few users who are registered. At the moment, anyone with a google account is able to login to the application. Instead of this, I would like the authentication to happen with google using OAuth2.0 and I would like to check if the user exists in my database before letting the user login to the system.
Update
Following is my code as requested
var passport = require('passport');
var GoogleStrategy = require('passport-google-oauth').OAuth2Strategy;
var config = require('./config');
var directoryService = require('./services/directory');
/**
* Authentication configuration
*/
module.exports = function (app, router) {
passport.serializeUser(function (user, done) {
//I want to know if this is the correct process
directoryService.findResidentByEmailAddress(user.emails[0].value).then(function (data) {
if (data == null || data.length == 0) {
done({ 'status': 'Invalid Login' });
} else {
done(null, data);
}
});
});
passport.deserializeUser(function (obj, done) {
done(null, obj);
});
passport.use(new GoogleStrategy({
clientID: config.auth.clientID,
clientSecret: config.auth.clientSecret,
callbackURL: config.auth.callbackURL,
passReqToCallback: true
},
function (request, accessToken, refreshToken, profile, done) {
process.nextTick(function () {
return done(null, profile);
});
}
));
app.use(passport.initialize());
app.use(passport.session());
router.use(function (req, res, next) {
if (req.isAuthenticated() || req.url.startsWith('/auth/')) {
return next();
}
res.redirect('/auth/login.html');
});
router.get('/auth/google',
passport.authenticate('google', { scope: ['email'] }));
router.get('/auth/google/callback',
passport.authenticate('google', { failureRedirect: '/login' }),
function (req, res) {
res.redirect('/');
});
router.get('/logout', function (req, res) {
req.logout();
res.redirect('/auth/login.html');
});
}