function boundAsyncFunctionConcurrency(f, N) {
  let waiting = [];
  let available = N;
  function lock() {
    if (available > 0) {
      --available;
      return;
    }
    return new Promise(res => {
      waiting.push(res);
    });
  }
  function unlock() {
    if (waiting.length > 0) {
      waiting.shift()();
    } else {
      ++available;
    }
  }

  return async function(...args) {
    try {
      await lock();
      return await f.apply(this, args);
    } finally {
      unlock();
    }
  };
}