'Register' route in Express.js not working

const express = require('express');

//import body-parser middleware
const bodyParser = require("body-parser");
const cookieParser = require("cookie-parser");

//list data
const names = [
    "Jack Bauer",
    "Jill Green",
    "John Joe",
    "Jonah Whale",
    "Jamaal LH",
    "Joe Fisher"
]


//Express launch function
const app = express();
//set the view engine to use pug for templating
app.set("view engine", "pug");


//use bodyParser and cookieParser middleware - third party.
app.use(bodyParser.urlencoded({extended: false}));
app.use(cookieParser());

const indexRouter = require("./routes");
const cardsRouter = require("./routes/cards");

app.use(indexRouter);
app.use(cardsRouter);

/*MIDDLEWARE*/

/* app.use((req, res, next) => {
    console.log("Hello");
    next();
 });

 app.use((req, res, next) => {
    console.log(", World");
    next();
 }); */

//404 Middleware!
app.use((res, req, next) => {
    const err = new Error('Page Not Found!');
    err.status = 404;
    next(err);
});

//error handler middleware
app.use((err, req, res, next) => {
    // do something
    //res.status(err.status)   
    res.locals.error = err;
    res.status(err.status);
    res.render('error');
    next();
    res.end();

 });

//Set up the development server listen method - port number
app.listen(3000, function(){
    console.log("server currently running on Heroku");

});

const express = require("express");
const routes = express.Router();

/*ROUTES*/

//serve the home route
routes.get('/', (req, res) => {

    const name = req.cookies.username;

    //basic response with the send method
    if(name) {        
        res.render('index', {name, page_title: "Flash Card App"});
    } else {
        res.redirect('/hello');
    }
     //res.end();
 });

//serve the register route
routes.get('/register', (req, res) => {

    //basic response with the send method
    res.render('register', {page_title: "Flash Card App: Register of users", names});
    //res.end();

 });

//serve the 4th route which will be a post route 
routes.get('/hello', (req, res) => {

    //store cookie
    const name = req.cookies.username;

    //perform actions based on setting of cookie
    if(name) {
        res.redirect('/');
    } else {
        res.render('hello', { page_title: "Flash Card App: Hello Route"});
    }

    //res.end();

 });

 routes.post('/hello', (req, res) => {

    const name = req.body.username;

    //basic response with the send method,
    res.cookie('username', name);
    res.redirect('/');

    //console.log(req.body);
    //res.end();

 });

 routes.post('/goodbye', (req, res) => {

    //res.clearCookie(req.cookies.username);
    res.clearCookie('username');
    res.redirect('/hello');
 });

 //export index routes to app.js
 module.exports = routes;

const express = require("express");
const routes = express.Router();

 //serve the cards route
 routes.get('/cards', (req, res) => {

    //basic response with the send method
     res.render('cards', {page_title: "Flash Card App", prompt: "Who is buried in Grant's tomb?"});
     //res.end();
 });


 //export cards routes to app.js
 module.exports = routes;