Add WebTorrent module

pkg/core/worker.go

@@ -0,0 +1,52 @@
+package core
+
+import (
+	"time"
+)
+
+type Worker struct {
+	timer *time.Timer
+	done  chan struct{}
+}
+
+// NewWorker run f after d
+func NewWorker(d time.Duration, f func() time.Duration) *Worker {
+	timer := time.NewTimer(d)
+	done := make(chan struct{})
+
+	go func() {
+		for {
+			select {
+			case <-timer.C:
+				if d = f(); d > 0 {
+					timer.Reset(d)
+					continue
+				}
+			case <-done:
+				timer.Stop()
+			}
+			break
+		}
+	}()
+
+	return &Worker{timer: timer, done: done}
+}
+
+// Do - instant timer run
+func (w *Worker) Do() {
+	if w == nil {
+		return
+	}
+	w.timer.Reset(0)
+}
+
+func (w *Worker) Stop() {
+	if w == nil {
+		return
+	}
+
+	select {
+	case w.done <- struct{}{}:
+	default:
+	}
+}