mongoose更新文档不工作

const mongoose = require('mongoose');

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

// 定义模型
const schema = new mongoose.Schema({
  name: String,
  age: Number,
});

const Model = mongoose.model('Model', schema);

// 查询文档
Model.findOne({ name: 'John' })
  .then((doc) => {
    if (doc) {
      // 更新文档
      doc.age = 30;
      return doc.save();
    }
  })
  .then(() => {
    console.log('Document updated successfully');
  })
  .catch((error) => {
    console.error('Error updating document', error);
  });