code: function _go() {
          if(workers < concurrency) {
              var job = queue.shift();
              if(job !== undefined) {
                  var worker = job.shift();
                  job.push(over);
                  workers++;
                  process.nextTick(function nextTickWorker() {
                      worker.apply(null, job);
                  });
                  return true;
              }
          }
          return false;
      }
docs: This function launches a new worker, if possible It returns true if a new worker was launched, false otherwise.