如何在我的Express路由器中使用两个MongoDB集合？

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

const mongoose = require('mongoose');

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

const productSchema = new mongoose.Schema({
  name: String,
  price: Number,
  description: String
});

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

const express = require('express');
const router = express.Router();

router.post('/users', (req, res) => {
  const newUser = new User({
    name: req.body.name,
    email: req.body.email,
    password: req.body.password
  });

  newUser.save()
    .then(user => {
      res.json(user);
    })
    .catch(err => {
      res.status(500).json({ error: err.message });
    });
});

router.post('/products', (req, res) => {
  const newProduct = new Product({
    name: req.body.name,
    price: req.body.price,
    description: req.body.description
  });

  newProduct.save()
    .then(product => {
      res.json(product);
    })
    .catch(err => {
      res.status(500).json({ error: err.message });
    });
});

module.exports = router;