type workerWrapper struct {
    worker        Worker
    interruptChan chan struct{}
    // reqChan is NOT owned by this type, it is used to send requests for work.
    reqChan chan<- workRequest
    // closeChan can be closed in order to cleanly shutdown this worker.
    closeChan chan struct{}
    // closedChan is closed by the run() goroutine when it exits.
    closedChan chan struct{}
}
func newWorkerWrapper(
    reqChan chan<- workRequest,
    worker Worker,
) *workerWrapper {
    w := workerWrapper{
        worker:        worker,
        interruptChan: make(chan struct{}),
        reqChan:       reqChan,
        closeChan:     make(chan struct{}),
        closedChan:    make(chan struct{}),
    }
    go w.run()
    return &w
}

func (w *workerWrapper) interrupt() {
    close(w.interruptChan)
    w.worker.Interrupt()
}

func (w *workerWrapper) run() {
    jobChan, retChan := make(chan interface{}), make(chan interface{})
    defer func() {
        w.worker.Terminate()
        close(retChan)
        close(w.closedChan)
    }()
    for {
        // NOTE: Blocking here will prevent the worker from closing down.
        w.worker.BlockUntilReady()
        select {
        case w.reqChan <- workRequest{
            jobChan:       jobChan,
            retChan:       retChan,
            interruptFunc: w.interrupt,
        }:
            select {
            case payload := <-jobChan:
                result := w.worker.Process(payload)
                select {
                case retChan <- result:
                case <-w.interruptChan:
                    w.interruptChan = make(chan struct{})
                }
            case _, _ = <-w.interruptChan:
                w.interruptChan = make(chan struct{})
            }
        case <-w.closeChan:
            return
        }
    }
}

func (w *workerWrapper) stop() {
    close(w.closeChan)
}

func (w *workerWrapper) join() {
    <-w.closedChan
}