mogoose错误{useNewUrlParser: true}{ useUnifiedTopology: true}

启动mongoose的时候，有一些警告信息

(node:10568) DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient const ..

(node:1920) DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.

修改如下后，就没有报错了。

mongoose.connect('mongodb://127.0.0.1:27017/app', { useNewUrlParser: true, useUnifiedTopology: true },function(err){
  if(err){
    //throw err;
    console.log(err);
  }else{
    console.log('数据库连接成功');
  }
});