docs: function timeout(req, delay) {
    setTimeout(_timeout, delay);
  
    function _timeout() {
      let callback = callbacks[req.id];
  
      if (!callback) return;
  
      let err = new Error("request timeout");
  
      err.name = "Timeout";
  
      callback(rpc.error(req, err).error);
  
      delete callbacks[req.id];
    }
  }