无法使用Node.js Express MongoDB Mongoose CoffeeScript进行POST

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/my_database', { useNewUrlParser: true });

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const MyModelSchema = new Schema({
  name: String,
  age: Number
});

module.exports = mongoose.model('MyModel', MyModelSchema);

const express = require('express');
const app = express();
const bodyParser = require('body-parser');
const MyModel = require('./models/my_model');

app.use(bodyParser.json());

app.post('/my_endpoint', (req, res) => {
  const newItem = new MyModel(req.body);
  newItem.save((err, item) => {
    if (err) {
      res.status(500).send(err);
    } else {
      res.status(201).send(item);
    }
  });
});

app.listen(3000, () => {
  console.log('Server started on port 3000');
});