title: Parse duplicate http headers from request in Node?
body: <p>In some special cases, there would exist http request headers which have duplicate values, such as XFF headers appended as following in header:
  <code>
  x-forwarded-for: *.*.*.*
  x-forwarded-for: *.*.*.*
  </code></p>
  
  <p>And by use of npm package express and request, could we parse the duplicate headers in following code?
  <code>
  req.headers['x-forwarded-for']
  </code></p>