code: function error(err) {
      if (done) return;
      done = true;
  
      // clean up
      cleanup();
      if (!self.headerSent) self.removeHeader('Content-Disposition');
  
      // callback available
      if (fn) return fn(err);
  
      // list in limbo if there's no callback
      if (self.headerSent) return;
  
      // delegate
      next(err);
    }
docs: errors