mapLimit of Generator doesn't invoke final callback

[mattoshry]

const assert = require('assert'),
  async = require('neo-async');

function *makeGen(arr) {
  let idx = 0;
  let len = arr.length;
  while (idx < len) {
    yield arr[idx];
    idx += 1;
  }
}

const LIMIT = 2;
const INPUT = ['abc', 'def', 'ghi', 'jkl'];
const gen = makeGen(INPUT);

async.mapLimit(gen, LIMIT, (v, cb) => {
  setTimeout(() => {
    console.log(`processing: ${v}`);
    cb(undefined, v);
  }, Math.round(Math.random()*1000));
}, (err, results) => {
  assert(!err, err);
  console.log(`ACTUAL: ${results}`);
  assert.strict.deepEqual(results, INPUT);
});

Results with neo-async:

processing: abc
processing: def
processing: jkl
processing: ghi

Results with async:

processing: abc
processing: def
processing: jkl
processing: ghi
ACTUAL: abc,def,ghi,jkl

[suguru03]

@mattoshry Thanks for the issue! I will take a look this weekend.