connect mongodb remote server to node js app

I have to connect node js app running on local machine(laptop) to mongodb running on deigtal ocean vps. I changed bindip in mongodb conf file. from local machine(laptop) the mongodb connection uri is below: mongodb://username:password@digital_ocean_server_ip:27017/animal

db.js

const mongoose = require("mongoose");
const connectDB = async (type = 0) => {
   try {
      //process.env.MONGO_URI is .env var which contains the DB URL
      const conn = await mongoose.connect(process.env.MONGO_URI, {
      useNewUrlParser: true,
      useUnifiedTopology: true,
   });
      console.log(`MongoDb Connected: ${conn.connection.host}`);
   } catch (err) {
      console.log(err);
      console.log("database connection error");
   }
};

module.exports = connectDB;

.env

 MONGO_URI=mongodb://username:password@digital_ocean_server_ip:27017/animal

app.js

//import db.js file in your app.js/index.js/server.js 
const connectdb = require("./db");
connectdb();