Can we remember the user outside a route in passport.js? - node.js

Question

I'm creating a MEAN Stack food catalog application. Node.js gives me the user logged in, in my login route when I check for req.isAuthenticated(). But when I try to check later whether I'm still logged in, it gives req.user as undefined.
How do I make the user persist? I know I can use local storage but is there a better way?
var express = require('express');
var cors = require('cors');
var bodyParser = require('body-parser');
var passport = require('passport');
var mongoose = require('mongoose');
var LocalStrategy = require('passport-local');
var passportLocalMongoose = require('passport-local-mongoose');
app = express();
app.use(require('express-session')({secret:"timelord",resave:false,saveUninitialized:false}));
app.use(cors());
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(passport.initialize());
app.use(passport.session());
mongoose.set('useNewUrlParser', true);
mongoose.set('useUnifiedTopology', true);
mongoose.connect('mongodb://127.0.0.1:27017/delectabledb');
var UserSchema = new mongoose.Schema({name: String,
gender: String,
dob: String,
country:String,
phone: String,
email: String,
password: String,
username: String,
prof: String});
UserSchema.plugin(passportLocalMongoose);
var User = mongoose.model("User", UserSchema);
passport.use(new LocalStrategy(User.authenticate()));
passport.serializeUser(User.serializeUser());
passport.deserializeUser(User.deserializeUser());
app.post('/loginUser', function(req, res, next) {
passport.authenticate('local', function(err, user, info) {
console.log(req.user) //returns false
if (err) { return next(err); }
if (!user) { res.send({code:"500"}); }
req.logIn(user, function(err) {
console.log(req.user) //returns true
if (err) { return next(err); }
res.send({code:"200", user:user});
});
})(req, res, next);
});
app.listen(3000, ()=>{
console.log("Running server on port 3000...");
});