问如何解决此错误: Route.get()需要回调函数，但获得了[object Undefined]

EN

// /middleware/authMiddleware.js 
'use strict'

const jwt = require('jwt-simple');
const moment = require('moment');
require('dotenv').config();


function isAuth(req,res, next) {
    if(!req.headers.authorization) {
        return res.status(403).send({mesagge: 'No tienes autorización'})
    }

    const token = req.headers.authorization.split(" ")[1];
    const payload = jwt.decode(token, process.env.JWT_SECRET_TOKEN);

    if(payload.exp <= moment().unix()) {
        return res.status(401).send({message: 'El token ha expirado'})
    }

    req.user = payload.sub;
    next();
}

module.exports = isAuth

'use strict'

const express = require('express');
const router = express.Router();
const authMiddleware  = require ('../middleware/authMiddleware');

/* GET home page. */
router.get('/', function(req, res, next) {
    res.render('index', { title: 'Express' });
});

router.get('/exito', authMiddleware.isAuth,  (req, res) => {
    return res.status(200).send({token: req.user})
});

module.exports = router;

Route.get() requires a callback function but got a [object Undefined]