code: func (h *NegotiationHandler) WriteCode(w http.ResponseWriter, r *http.Request, code int, e interface{}) {
  	switch httputil.NegotiateContentType(r, []string{}, "application/json") {
  	case "text/html":
  		h.html.WriteCode(w, r, code, e)
  		return
  	case "text/plain":
  		h.plain.WriteCode(w, r, code, e)
  		return
  	case "application/json":
  		h.json.WriteCode(w, r, code, e)
  		return
  	default:
  		h.json.WriteCode(w, r, code, e)
  		return
  	}
  }
docs: // WriteCode writes a response object to the ResponseWriter and sets a response code.