How to connect to the database:mongoose?

Below is my code:The folder and filename is : gridFs/storeAudio.js.And the code is in storeAudio.js

var mongoose = require('mongoose');
var fs = require('fs');
var Grid = require('gridfs-stream');
Grid.mongo=mongoose.mongo;


//establish mongoDB connection

var conn = mongoose.createConnection('mongodb://localhost:27017/aHolyBoly');
conn.once('open',function(){
  //  var gfs = Grid(conn.db);
 // var db = new mongo.Db('aHolyBoly', new mongo.Server("127.0.0.1", 27017));
//var gfs = Grid(db, mongo);

var writeStream = gfs.createWriteStream({
    filename:'song1.mp3'
});
fs.createReadStream('../list/hero.mp3').pipe(writeStream);
writeStream.on('close',function(file){
    console.log(file.filename +'Written to db');
});
});

now in the cmd inside the gridFs file I am running the command node storeAudio.js to create the database with the collection.But the following error is displayed below in the screenshot attached:

Note:I ran the following commands before:npm install gridfs-stream,npm install mongoose.

Please let me know if any more inputs are needed.

via Aditya Jain