Stream file and create a local buffer, after stream ends, use the buffer accordingly

streamFile.js

const readStream = s3Mumbai.getObject(workbookfile).createReadStream();
const buffers = [];

readStream.on('data', data => {
  buffers.push(data);
});

readStream.on('error', err => {
  next(err);
});

readStream.on('end', () => {
  const buffer = Buffer.concat(buffers);
  // here you can convert your buffer to any other data type
  // and here you call the next function you want to call
  // after the whole file is loaded in the memory
  next(null, buffer);
});