Issues while trying to add attachment through API - Javascript

I am trying to call /attachments endpoint to post new attachment to the issue. However, I am keep getting errors. First error that I am getting is statusText: ‘Unsupported Media Type’,
then I’ve also tried adding ‘Content-type’ header but it then gives me error 500."/attachment", multer().single("file"), async (req, res) => {

  fetch("http://localhost:8080/rest/api/latest/issue/DP-2/attachments", {
    method: "POST",
    body: req.file,
    headers: {
      Authorization: "Basic xxx",
      "X-Atlassian-Token": "no-check",
    .then((res) => console.log(res))
    .then((result) => res.json(result))
    .catch((err) => console.log(err));

This is called from my node.js server to avoid cors issue. To make it more clear here is what is passed to the req.file:

  fieldname: 'file',
  originalname: 'file.txt',
  encoding: '7bit',
  mimetype: 'text/plain',
  buffer: <Buffer 74 65 73 74 73 65 74 65 73 74 73 74 65 74>,
  size: 14

It works fine with the Postman, but not in browser. Appreciate any help.