I am trying to create a login page and sign up page, my app.js gives me this error, I think it is the last line of this code. I can send you the other components(files) for this express app. I cannot understand what is causing this error.

const express = require('express');
const mongoose = require('mongoose');
// Routes
const authRoutes = require('./routes/authRoutes');

const app = express();

// middleware
app.use(express.static('public'));

app.use((err, req, res, next) => {
  res.locals.error = err;
  res.status(err.status);
  res.render('error');
});

// view engine
app.set('view engine', 'ejs');

// database connection
const dbURI = '<database, username and password>';
mongoose.connect(dbURI, { useNewUrlParser: true, useUnifiedTopology: true, useCreateIndex:true })
  .then((result) => app.listen(3000))
  .catch((err) => console.log(err));

// routes
app.get('/', (req, res) => res.render('home'));
app.get('/smoothies', (req, res) => res.render('smoothies'));
app.use(authRoutes);

authRoutes.js

const { Router } = require('express')
const authController = require('./authController.js')
 
const router = Router();

router.get('/signup', authController.signup_get);
router.get('/signup', authController.signup_post);
router.get('/login', authController.login_get);
router.get('/login', authController.login_post);

module.export = router;

authController.js

module.exports.signup_get = (req, res) => {
  res.render('signup');  
}

module.exports.login_get = (req, res) => {
    res.render('login');  
}

module.exports.signup_post = (req, res) => {
    res.send('signup');  
}

module.exports.login_post = (req, res) => {
    res.send('login');  
}