code: function async(fn) {
    return function asynced(done) {
      var err, ret;
      try {
        ret = fn();
      } catch (e) {
        err = e;
      } finally {
        if (err) {
          done(err);
        } else {
          done(null, ret);
        }
      }
    };
  }
docs: Transform a synchronous function into an asynchronous one.