header.go
func (h *RequestHeader) CookieBytes(key []byte) []byte {
	h.parseRawHeaders()
	h.collectCookies()
	return peekArgBytes(h.cookies, key)
}
func (h *RequestHeader) CookieBytes(key []byte) []byte {
	h.parseRawHeaders()
	h.collectCookies()
	return peekArgBytes(h.cookies, key)
}
// CookieBytes returns cookie for the given key.