header.go
func (h *RequestHeader) SetCookieBytesK(key []byte, value string) {
	h.SetCookie(b2s(key), value)
}
func (h *RequestHeader) SetCookieBytesK(key []byte, value string) {
	h.SetCookie(b2s(key), value)
}
// SetCookieBytesK sets 'key: value' cookies.