code: func (h *HTTPBin) CacheControl(w http.ResponseWriter, r *http.Request) {
  	parts := strings.Split(r.URL.Path, "/")
  	if len(parts) != 3 {
  		http.Error(w, "Not found", http.StatusNotFound)
  		return
  	}
  
  	seconds, err := strconv.ParseInt(parts[2], 10, 64)
  	if err != nil {
  		http.Error(w, err.Error(), http.StatusBadRequest)
  		return
  	}
  
  	w.Header().Add("Cache-Control", fmt.Sprintf("public, max-age=%d", seconds))
  	h.Get(w, r)
  }
docs: // CacheControl sets a Cache-Control header for N seconds for /cache/N requests