func (h *reqHandler) getUpstreamReader(start, end uint64) io.ReadCloser {
	subh := *h
	subh.req = subh.getNormalizedRequest()
	subh.req.Header.Set("Range", fmt.Sprintf("bytes=%d-%d", start, end))

	h.Logger.Debugf("[%p] Making upstream request for %s, bytes [%d-%d]...",
		subh.req, subh.req.URL, start, end)

	//!TODO: optimize requests for the same pieces? if possible, make only 1 request to the upstream for the same part

	r, w := io.Pipe()
	subh.resp = httputils.NewFlexibleResponseWriter(func(rw *httputils.FlexibleResponseWriter) {
		respRng, err := httputils.GetResponseRange(rw.Code, rw.Headers)
		if err != nil {
			h.Logger.Debugf("[%p] Could not parse the content-range for the partial upstream request: %s", subh.req, err)
			_ = w.CloseWithError(err)
		}
		h.Logger.Debugf("[%p] Received response with status %d and range %v", subh.req, rw.Code, respRng)
		if rw.Code == http.StatusPartialContent {
			//!TODO: check whether the returned range corresponds to the requested range
			rw.BodyWriter = w
		} else if rw.Code == http.StatusOK {
			//!TODO: handle this, use skipWriter or something like that
			_ = w.CloseWithError(fmt.Errorf("NOT IMPLEMENTED"))
		} else {
			_ = w.CloseWithError(fmt.Errorf("Upstream responded with status %d", rw.Code))
		}
	})
	go utils.SafeExecute(
		subh.carbonCopyProxy,
		func(err error) {
			h.Logger.Errorf("[%p] Panic inside carbonCopyProxy %s", subh.req, err)
			w.CloseWithError(err) // !TODO maybe some other error
		},
	)
	return newWholeChunkReadCloser(r, h.Cache.PartSize.Bytes())
}
func safeExecute(f func(), key types.ObjectIDHash) {
	utils.SafeExecute(f, func(err error) {
		log.Printf("panic inside the function for key '%s' : %s", key, err)
	})
}