Using aggregate in mongoose 4.x with Mongodb 3.6

gistfile1.txt

return new Promise((resolve, reject) => {
      var allResultsCursor = this.model('Combined').aggregate([{
          // $match object
          // $lookup
          // $unwind
          // $group
          // $project

       ]).cursor({ batchSize: 1000 })
                      .exec();

        var  resultPayload = [];
         allResultsCursor.eachAsync(result => {	    // loop thru and colllect result        	
              resultPayload.push(result);            	
         })
         .then(() => {
             resolve(resultPayload) ;            	// resolve with the final payload
          })
          .catch(err => reject(err)); 
});