header.go
func (h *RequestHeader) SetHostBytes(host []byte) {
	h.parseRawHeaders()
	h.host = append(h.host[:0], host...)
}
func (h *RequestHeader) SetHostBytes(host []byte) {
	h.parseRawHeaders()
	h.host = append(h.host[:0], host...)
}
// SetHostBytes sets Host header value.