code: function whilst(test, iteratee, callback) {
      callback = onlyOnce(callback);
      var _fn = wrapAsync(iteratee);
      var _test = wrapAsync(test);
      var results = [];
  
      function next(err, ...rest) {
          if (err) return callback(err);
          results = rest;
          if (err === false) return;
          _test(check);
      }
  
      function check(err, truth) {
          if (err) return callback(err);
          if (err === false) return;
          if (!truth) return callback(null, ...results);
          _fn(next);
      }
  
      return _test(check);
  }
docs: Repeatedly call `iteratee`, while `test` returns `true`. Calls `callback` when
  stopped, or an error occurs.
  
  @name whilst
  @static
  @memberOf module:ControlFlow
  @method
  @category Control Flow
  @param {AsyncFunction} test - asynchronous truth test to perform before each
  execution of `iteratee`. Invoked with ().
  @param {AsyncFunction} iteratee - An async function which is called each time
  `test` passes. Invoked with (callback).
  @param {Function} [callback] - A callback which is called after the test
  function has failed and repeated execution of `iteratee` has stopped. `callback`
  will be passed an error and any arguments passed to the final `iteratee`'s
  callback. Invoked with (err, [results]);
  @returns {Promise} a promise, if no callback is passed
  @example
  
  var count = 0;
  async.whilst(
  function test(cb) { cb(null, count < 5;) },
  function iter(callback) {
  count++;
  setTimeout(function() {
  callback(null, count);
  }, 1000);
  },
  function (err, n) {
  // 5 seconds have passed, n = 5
  }
  );