header.go
func (h *ResponseHeader) SetCookie(cookie *Cookie) {
	h.cookies = setArgBytes(h.cookies, cookie.Key(), cookie.Cookie(), argsHasValue)
}
func (h *ResponseHeader) SetCookie(cookie *Cookie) {
	h.cookies = setArgBytes(h.cookies, cookie.Key(), cookie.Cookie(), argsHasValue)
}
// SetCookie sets the given response cookie.
//
// It is save re-using the cookie after the function returns.