tunny.go
func New(n int, ctor func() Worker) *Pool {
	p := &Pool{
		ctor:    ctor,
		reqChan: make(chan workRequest),
	}
	p.SetSize(n)

	return p
}
func New(n int, ctor func() Worker) *Pool {
	p := &Pool{
		ctor:    ctor,
		reqChan: make(chan workRequest),
	}
	p.SetSize(n)

	return p
}
// New creates a new Pool of workers that starts with n workers. You must
// provide a constructor function that creates new Worker types and when you
// change the size of the pool the constructor will be called to create each new
// Worker.