http.go
func (resp *Response) BodyWriteTo(w io.Writer) error {
	if resp.bodyStream != nil {
		_, err := copyZeroAlloc(w, resp.bodyStream)
		resp.closeBodyStream()
		return err
	}
	_, err := w.Write(resp.bodyBytes())
	return err
}
func (resp *Response) BodyWriteTo(w io.Writer) error {
	if resp.bodyStream != nil {
		_, err := copyZeroAlloc(w, resp.bodyStream)
		resp.closeBodyStream()
		return err
	}
	_, err := w.Write(resp.bodyBytes())
	return err
}
// BodyWriteTo writes response body to w.