how to make post request for transfer file by electron net module?

In the absence of other third-party libraries(e.g node-fetch、axios、form-data) how to make post request for transfer file by electron net module? I already know how to post data,like this:

request = net.request({
    url: 'http://localhost/xxx',
    method: 'POST'
})
request.on('response', (response) => {
    console.log(`STATUS: ${response.statusCode}`)
    console.log(`HEADERS: ${JSON.stringify(response.headers)}`)
    response.on('data', (chunk) => {
        console.log(`BODY: ${chunk}`)
    })
    response.on('end', () => {
        console.log('No more data in response.')
    })
})
request.write(data)
request.end()

but,idont know how to process formdata(origin formdata from XMLHttpRequest,not npm form-data lib),such as:

var formData = new FormData();
var myFile = document.getElementById("myFileInput");
formData.append('myFile',myFile.files[0]);

request.write(data) need the data type is string or an instance of Buffer or unit8Array,i dont know how to convert data to this type