Using multer memory storage to send uploaded image to external services

I am currently using Multer to handle my image uploads and I am using multer's memory storage option to write the image to the buffer. I would like to then retrieve this image buffer and send it to an external service like Mircosoft Cognitive Services. However, whenever I send the image buffer to cognitive services, it appears that only part of the whole image buffer is sent. How do I ensure that I have read the whole image buffer into a variable first before sending it to cognitive services? My existing code looks something like this:

var multer = require('multer');
var upload = multer({ storage: multer.memoryStorage() });

//Upload route
router.route('/uploadImage')
  .post(upload.single('profileImg'), function(req, res, next){
    //Store image upload buffer in variable
    var img = req.file.buffer;
    
    //Send the image upload buffer stored in variable to cognitive services
    request.post({
      ...,
      body: img //Should be complete when sent to cognitive services
    })
  });

via Chua Bing Quan