code: func getRequestHeaders(r *http.Request) http.Header {
  	h := r.Header
  	h.Set("Host", r.Host)
  	return h
  }
docs: // requestHeaders takes in incoming request and returns an http.Header map
  // suitable for inclusion in our response data structures.
  //
  // This is necessary to ensure that the incoming Host header is included,
  // because golang only exposes that header on the http.Request struct itself.