在Mongoose的自定义回调中使用express响应

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

const app = express();

mongoose.connect('mongodb://localhost/mydatabase', { useNewUrlParser: true, useUnifiedTopology: true })
  .then(() => {
    console.log('Connected to MongoDB');
  })
  .catch((error) => {
    console.error('Error connecting to MongoDB', error);
  });

const userSchema = new mongoose.Schema({
  name: String,
  email: String,
});

const User = mongoose.model('User', userSchema);

const customCallback = (error, result) => {
  if (error) {
    res.status(500).send('An error occurred');
  } else {
    res.json(result);
  }
};

app.get('/users', (req, res) => {
  User.find({}, customCallback);
});