add Semaphore

Author: markus621

control/semaphore.go

@@ -0,0 +1,25 @@
+package control
+
+type (
+	Semaphore interface {
+		Acquire()
+		Release()
+	}
+	_semaphore struct {
+		c chan struct{}
+	}
+)
+
+func NewSemaphore(count uint64) Semaphore {
+	return &_semaphore{
+		c: make(chan struct{}, count),
+	}
+}
+
+func (s *_semaphore) Acquire() {
+	s.c <- struct{}{}
+}
+
+func (s *_semaphore) Release() {
+	<-s.c
+}