header.go
func (h *RequestHeader) SetRequestURI(requestURI string) {
	h.requestURI = append(h.requestURI[:0], requestURI...)
}
func (h *RequestHeader) SetRequestURI(requestURI string) {
	h.requestURI = append(h.requestURI[:0], requestURI...)
}
// SetRequestURI sets RequestURI for the first HTTP request line.
// RequestURI must be properly encoded.
// Use URI.RequestURI for constructing proper RequestURI if unsure.