Show HN: Golang Throttler – smart WaitGroups to easily manage worker goroutines

This is my first time posting code to Hacker News. I'd love to get any feedback on the quality and usefulness of the code as a package.

Throttler fills the gap between sync.WaitGroup and manually monitoring your goroutines with channels. The API is almost identical to Wait Groups, but it allows you to set a max number of workers that can be running simultaneously. It uses channels internally to block until a job completes by calling Done() or until all jobs have been completed.

See a fully functional example on the playground at http://bit.ly/throttler-docs

camlistore has a syncutil package (godoc.org/camlistore.org/pkg/syncutil) that has similar features, albeit in different structures:

- Gate is used to limit the number of parallel workers

- Group is used where sync.WaitGroup would be used. The most important thing: you have access to the error that happened in your goroutines.

Here's how to use it:

  var g = syncutil.NewGate(num_parallel_workers)

  for _, job := range jobs {
    wg.Go(func() error {
      defer g.Done()
      // do some long-running job

      // the job may fail
      return errJob
    })
  }

  return wg.Err()

  // You also have access to failing goroutines through wg.Errs()

looks useful, just my 2 cents