how to add file with formData in axios request using node.js

Question

I'm currently building my first npm package which contain axios requests. There is something wrong when i want to add a file as a parameter in a request and i don't know why.

I'm using form-data library and fs to add my local file.

First i created an abstract class to add my token in a header for every requests and a post method that will be used by my other classes :

import axios from 'axios'
import url from '../utils/constants.js'

class ApiBase {
  constructor(apiKey) {
    if (this.constructor === ApiBase) {
      throw new TypeError('Abstract class "ApiBase" cannot be instantiated directly');
    };

    let service = axios.create({
      headers: {
        'Authorization' : `Bearer ${apiKey}`
      },
    })
    
    this.service = service
  }

  post(payload, path) {
    return this.service.request({
      method: 'POST',
      url: url + path,
      data: payload
    })
  }
}
export default ApiBase

My class which extends ApiBase :

import ApiBase from "./api_base.js";
import { default as FormData } from "form-data"

class MyClass extends ApiBase {
  constructor(apiKey) {
    super(apiKey)
  }

  formatData (files, providers, language) {
    const user = new FormData();
      const key = [
        "files",
        "providers",
        "language",
      ];
      const value = [
        files,
        JSON.stringify(providers),
        language
      ];
      for (let i = 0; i < value.length; i++) {
        user.append(key[i], value[i]);
      }
    return user  
  }

  myFeature = (files, providers, language) => {
    const userData = this.formatData(files, providers, language);
    return this.post(userData, 'endpointApi')
  }

}

export default MyClass

Then i call myFeature in index.js to test it and try to console.log the api response :

import MyClass from './api/myclass.js'
import * as fs from 'fs';

const testFeature = new MyClass('MYAPIKEY')
var myFile = fs.createReadStream('./testData/Doc.jpg');
testFeature.myFeature(myFile,['microsoft'], "fr-FR").then((response) => {
  console.log(response.data)
})
.catch((error) => {
  console.log(error.response.data);
});

When i send request with other features that not need files it works...

Maybe something went wrong with formData or something missing in the headers