formidable: fileWriteStreamHandle doesn't call the passed function in express

Avantages

const { PassThrough } = require("stream");
const aws = require("aws-sdk");

const s3 = new aws.S3({
  apiVersion: "2006-03-01",
  accessKeyId: process.env.AWS_ACCESS_KEY_ID,
  secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
});


function uploadFile(req, res, next) {

  const uploadStream = (filename) => {
    const pass = PassThrough();
    
    /* This method is not being called*/
    console.log('uploadStream() called);

    s3.upload(
        {
        Bucket: process.env.AWS_BUCKET,
        Key: filename,
        Body: pass,
        },
        (err, data) => {
        console.log(err, data);
        if (err) {
            console.log(err);
        }
        console.log(data);
        }
    );
    
    return pass;
  };

  var form = formidable({
    maxFileSize: 5 * 1024 * 1024,
    minFileSize: 1,
    allowEmptyFiles:false,
    fileWriteStreamHandler: uploadStream // This method is not being called
  });
}

I have followed the example in link https://github.com/node-formidable/formidable/blob/master/examples/store-files-on-s3.js