尝试使用express-fileupload上载文件时将req.files获取为null

Question

我正在尝试使用express-fileupload上传文件。但是我将req.files设置为null，但是req.body正确给出了文件信息。

app.js

const express = require('express');
const fileUpload = require('express-fileupload');
const app = express();
app.use(fileUpload());
app.post('/upload', (req, res, next) => {
    console.log("req files", req.files);
    res.send("Send");
});

HTML表单

<form method="POST" enctype="multipart/form-data" action="/upload">
                    <div class="custom-file">
                        <input type="file" class="custom-file-input" id="customFile" name="file" required>
                        <label class="custom-file-label" for="customFile">Choose file</label>
                    </div>
                    <div class="d-flex mt-3">
                        <button type="submit" class="btn btn-primary ml-auto">Upload to database</button>
                    </div>
</form>

上面的代码有什么问题？