Запрос перекрестного происхождения заблокировал Node Js с атласом mongodb

Question

Я просматриваю грубое руководство по node.js и mongodb Atlas, и когда я пытаюсь отправить запрос на создание пользователя на сервер, я получаю ошибку Cors-источника.

Я поставил требование cors, и app.use в моем server.js есть что-то еще, что мне нужно сделать?

Вот ошибка:

Блокировка перекрестного запроса: та же политика происхождения запрещает чтение удаленного ресурса на http://localhost:5000/users/. (причина: запрос CORS не выполнен).

Server.js

const express = require('express');
const cors = require('cors');
const mongoose = require('mongoose');

require('dotenv').config();

const app = express();
const port = process.env.PORT || 5000;

app.use(cors());
app.use(express.json());

const uri = process.env.ATLAS_URI;
mongoose.connect(uri, { useNewUrlParser: true, useCreateIndex: true });
const connection = mongoose.connection;
connection.once('open', () => {
  console.log("MongoDB database connection established successfully");
})

const exercisesRouter = require('./routes/exercises');
const usersRouter = require('./routes/users');

app.use('/exercises', exercisesRouter);
app.use('/users', usersRouter);

app.listen(port, () => {
  console.log(`Server is running on port: ${port}`);
});

users.js

const router = require('express').Router();
let User = require('../models/user.model');

router.route('/').get((req, res) => {
  User.find()
   .then(users => res.json(users))
    .catch(err => res.status(400).json('Error: ' + err));
});

router.route('/add').post((req, res) => {
  const username = req.body.username;

  const newUser = new User({username});

  newUser.save()
    .then(() => res.json('User added!'))
    .catch(err => res.status(400).json('Error: ' + err));
});

module.exports = router;

Вот что я получаю в браузере:

{username: "wwewe"}
username: "wwewe"
__proto__:
constructor: ƒ Object()
hasOwnProperty: ƒ hasOwnProperty()
isPrototypeOf: ƒ isPrototypeOf()
propertyIsEnumerable: ƒ propertyIsEnumerable()
toLocaleString: ƒ toLocaleString()
toString: ƒ toString()
valueOf: ƒ valueOf()
__defineGetter__: ƒ __defineGetter__()
__defineSetter__: ƒ __defineSetter__()
__lookupGetter__: ƒ __lookupGetter__()
__lookupSetter__: ƒ __lookupSetter__()
get __proto__: ƒ __proto__()
set __proto__: ƒ __proto__()
xhr.js:166 OPTIONS http://localhost:5000/users/add          
net::ERR_CONNECTION_REFUSED
dispatchXhrRequest  @   xhr.js:166
xhrAdapter  @   xhr.js:16
dispatchRequest @   dispatchRequest.js:49
Promise.then (async)        
request @   Axios.js:56
Axios.<computed>    @   Axios.js:80
wrap    @   bind.js:11
onSubmit    @   create-user.component.js:31
callCallback    @   react-dom.development.js:363
invokeGuardedCallbackDev    @   react-dom.development.js:412
invokeGuardedCallback   @   react-dom.development.js:466
invokeGuardedCallbackAndCatchFirstError @   react-dom.development.js:481
executeDispatch @   react-dom.development.js:614
executeDispatchesInOrder    @   react-dom.development.js:639
executeDispatchesAndRelease @   react-dom.development.js:744
executeDispatchesAndReleaseTopLevel @   react-dom.development.js:753
forEachAccumulated  @   react-dom.development.js:725
runEventsInBatch    @   react-dom.development.js:770
runExtractedPluginEventsInBatch @   react-dom.development.js:916
handleTopLevel  @   react-dom.development.js:6171
batchedEventUpdates @   react-dom.development.js:2422
dispatchEventForPluginEventSystem   @   react-dom.development.js:6271
dispatchEvent   @   react-dom.development.js:6301
unstable_runWithPriority    @   scheduler.development.js:674
runWithPriority$2   @   react-dom.development.js:11834
discreteUpdates$1   @   react-dom.development.js:22935
discreteUpdates @   react-dom.development.js:2440