Content-type cannot be modified during POST?

  node.js, question
require('request');
 headers: {
 'content-type':'application/x-www-form-urlencoded;  charset=UTF-8'
 bracket

Actual value obtained:

Content-Type: multipart/form-data;  boundary=--------------------------968457475602141625142157

It is suggested to change to HTTP standardContent-TypeTry again,requestThis package only seems to escape the camel-case key