diff --git a/util/semaphore.go b/util/semaphore.go
new file mode 100644
index 0000000..2a0d509
--- /dev/null
+++ b/util/semaphore.go
@@ -0,0 +1,17 @@
+package util
+
+type Semaphore struct {
+	c chan struct{}
+}
+
+func NewSemaphore(cap int) Semaphore {
+	return Semaphore{make(chan struct{}, cap)}
+}
+
+func (s Semaphore) Down() {
+	s.c <- struct{}{}
+}
+
+func (s Semaphore) Up() {
+	<-s.c
+}