node.js-CORS问题：无法使用NodeJs和Angular发送post请求

我在尝试发送post请求时收到以下消息：

Access to XMLHttpRequest at 'http://localhost:3002/api/products/checkout' from origin 
'http://localhost:4200' has been blocked by CORS policy: Request header field content-type 
is not allowed by Access-Control-Allow-Headers in preflight response.

现在，我只是尝试将数据发送到后端，然后将其登录到控制台。Get请求工作正常，但由于某种原因，我在尝试发布时遇到了CORS错误。这是我的代码：

角度代码：

//api call
return this.http.post('http://localhost:3000/api/checkout', cart)

NodeJs代码：

const bodyParser = require('body-parser');
const express = require('express');

const app = express();

app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));

app.use((req, res, next) => {
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader(
        'Access-Control-Allow-Header', 
        'Origin, X-Requested-With, Content-Type, Accept');
    res.setHeader(
        'Access-Control-Allow-Methods', 
        'GET, POST, PATCH, DELETE, OPTIONS');
    next();
})

app.post("/api/checkout", (req, res, next) => {
    const cart = req.body;
    console.log(cart)
    res.status(201).json()
})

module.exports = app;