connect.sid not getting stored in cookie

I have a node express application.

const session = require('express-session');
const config = require('config');
var MemoryStore = require('memorystore')(session);


module.exports = function (app) {
    app.use(express.json());
    app.use(
        session({
            saveUninitialized: false,
            cookie: { maxAge: 86400000 },
            store: new MemoryStore({
                checkPeriod: 86400000
            }),
            resave: false,
            secret: config.get('Storagehash')
        })
    );
    app.use('/api/auth', users);
}

I have separated auth route and put it in a separate file like this. When I do console.log(req.session) I'm getting proper output.

const router = express.Router();


router.post('/', async (req, res) => {

....
    req.session.isAuth = true;    
    console.log(req.session);
    req.session.customerID = customer;
 
    res.send(token);


}

But when I'm looking in the cookie tab, connect.sid is not getting inserted there.