// setupRewindBody returns a new request with a custom body wrapper
// that can report whether the body needs rewinding.
// This lets rewindBody avoid an error result when the request
// does not have GetBody but the body hasn't been read at all yet.
func setupRewindBody(req *Request) *Request {
	if req.Body == nil || req.Body == NoBody {
		return req
	}
	newReq := *req
	newReq.Body = &readTrackingBody{ReadCloser: req.Body}