code: function queue(task, done) {
      var storage = this,
          key = this.keygen(task);
  
      // store task as JSON serialized string
      task = JSON.stringify(task);
  
      // first add the key to the queue
      this.redis().rpush(this.queueKey(), key, function(err) {
          if (err) done(err);
  
          // now store task data
          else storage.redis().set(key, task, function(err) {
              if (err) done(err);
              else done(null, key);
          });
      });
  }
docs: Queue a serialized request and pass the storage key to the callback.
  @param {object} task
  @param {function} done