diff --git a/concurrent/gater.go b/concurrent/gater.go
index 540d1ce..f9d4d21 100644
--- a/concurrent/gater.go
+++ b/concurrent/gater.go
@@ -1,16 +1,44 @@
 package concurrent
 
-// Gater 用于控制最大并发协程数
-type Gater chan struct{}
+import (
+	"sync"
 
-func NewGater(cap int) Gater {
-	return make(Gater, cap)
+	"github.com/pyihe/go-pkg/maths"
+)
+
+type Limiter struct {
+	queue  chan struct{}
+	waiter *sync.WaitGroup
 }
 
-func (g Gater) Enter() {
-	g <- struct{}{}
+func NewLimiter(size int) *Limiter {
+	size = maths.MaxInt(0, size)
+	return &Limiter{
+		queue:  make(chan struct{}, size),
+		waiter: &sync.WaitGroup{},
+	}
 }
 
-func (g Gater) Leave() {
-	<-g
+func (lim *Limiter) Add(delta int) {
+	switch {
+	case delta > 0:
+		for i := 0; i < delta; i++ {
+			lim.queue <- struct{}{}
+		}
+	default:
+		for i := 0; i > delta; i-- {
+			<-lim.queue
+		}
+	}
+
+	lim.waiter.Add(delta)
+}
+
+func (lim *Limiter) Done() {
+	<-lim.queue
+	lim.waiter.Done()
+}
+
+func (lim *Limiter) Wait() {
+	lim.waiter.Wait()
 }