diff --git a/pool.go b/pool.go
index fbf3b80..b4e8f34 100644
--- a/pool.go
+++ b/pool.go
@@ -48,7 +48,7 @@ type Pool struct {
 	workers []*Worker
 
 	// release is used to notice the pool to closed itself.
-	release chan sig
+	release bool
 
 	// lock for synchronous operation.
 	lock sync.Mutex
@@ -72,7 +72,7 @@ func (p *Pool) periodicallyPurge() {
 		currentTime := time.Now()
 		p.lock.Lock()
 		idleWorkers := p.workers
-		if len(idleWorkers) == 0 && p.Running() == 0 && p.release != nil {
+		if len(idleWorkers) == 0 && p.Running() == 0 && p.release {
 			p.lock.Unlock()
 			return
 		}
@@ -122,11 +122,12 @@ func NewTimingPool(size, expiry int) (*Pool, error) {
 
 // Submit submits a task to this pool.
 func (p *Pool) Submit(task f) error {
-	if p.release != nil {
+	if worker := p.getWorker(); worker != nil {
+		worker.task <- task
+		return nil
+	} else {
 		return ErrPoolClosed
 	}
-	p.getWorker().task <- task
-	return nil
 }
 
 // Running returns the number of the currently running goroutines.
@@ -159,8 +160,8 @@ func (p *Pool) ReSize(size int) {
 // Release Closes this pool.
 func (p *Pool) Release() error {
 	p.once.Do(func() {
-		p.release = make(chan sig)
 		p.lock.Lock()
+		p.release = true
 		idleWorkers := p.workers
 		for i, w := range idleWorkers {
 			w.task <- nil
@@ -191,6 +192,11 @@ func (p *Pool) getWorker() *Worker {
 
 	p.lock.Lock()
 	defer p.lock.Unlock()
+
+	if p.release {
+		return nil
+	}
+
 	idleWorkers := p.workers
 	n := len(idleWorkers) - 1
 	if n < 0 {
diff --git a/pool_func.go b/pool_func.go
index 0205ab1..ddf3034 100644
--- a/pool_func.go
+++ b/pool_func.go
@@ -46,7 +46,7 @@ type PoolWithFunc struct {
 	workers []*WorkerWithFunc
 
 	// release is used to notice the pool to closed itself.
-	release chan sig
+	release bool
 
 	// lock for synchronous operation.
 	lock sync.Mutex
@@ -73,7 +73,7 @@ func (p *PoolWithFunc) periodicallyPurge() {
 		currentTime := time.Now()
 		p.lock.Lock()
 		idleWorkers := p.workers
-		if len(idleWorkers) == 0 && p.Running() == 0 && p.release != nil {
+		if len(idleWorkers) == 0 && p.Running() == 0 && p.release {
 			p.lock.Unlock()
 			return
 		}
@@ -124,11 +124,12 @@ func NewTimingPoolWithFunc(size, expiry int, f pf) (*PoolWithFunc, error) {
 
 // Serve submits a task to pool.
 func (p *PoolWithFunc) Serve(args interface{}) error {
-	if p.release != nil {
+	if worker := p.getWorker(); worker != nil {
+		worker.args <- args
+		return nil
+	} else {
 		return ErrPoolClosed
 	}
-	p.getWorker().args <- args
-	return nil
 }
 
 // Running returns the number of the currently running goroutines.
@@ -161,8 +162,8 @@ func (p *PoolWithFunc) ReSize(size int) {
 // Release Closed this pool.
 func (p *PoolWithFunc) Release() error {
 	p.once.Do(func() {
-		p.release = make(chan sig)
 		p.lock.Lock()
+		p.release = true
 		idleWorkers := p.workers
 		for i, w := range idleWorkers {
 			w.args <- nil
@@ -193,6 +194,11 @@ func (p *PoolWithFunc) getWorker() *WorkerWithFunc {
 
 	p.lock.Lock()
 	defer p.lock.Unlock()
+
+	if p.release {
+		return nil
+	}
+
 	idleWorkers := p.workers
 	n := len(idleWorkers) - 1
 	if n < 0 {