A generic goroutine pool just like Python ThreadPoolExecutor.

Gool provides the following methods:

• Submit: Submit a task and return the result (if any).
• AsyncSubmit: Submit a task and return a future of the result (if any), the future is actually the result channel.
• Map: Submit a bundle of tasks and return the results in order (if any).
• AsyncMap: Submit a bundle of tasks and return the futures of the results (if any), the futures are the result channels.

To use Gool, you need to define:

• Handler function: handler func(A) R, and
• Argument: arg A

With types A and R being arbitrary types.

You can also specify the number of workers numWorkers and the task queue size cap when creating a new pool.