diff --git a/queue.go b/queue.go
index 45ad1d1..d5ec5a5 100644
--- a/queue.go
+++ b/queue.go
@@ -251,6 +251,16 @@ func (q *Queue) start() {
 	tasks := make(chan core.QueuedMessage, 1)
 
 	for {
+		// check worker number
+		q.schedule()
+
+		select {
+		// wait worker ready
+		case <-q.ready:
+		case <-q.quit:
+			return
+		}
+
 		// request task from queue in background
 		q.routineGroup.Run(func() {
 			for {
@@ -289,11 +299,6 @@ func (q *Queue) start() {
 			return
 		}
 
-		// check worker number
-		q.schedule()
-		// wait worker ready
-		<-q.ready
-
 		// start new task
 		q.metric.IncBusyWorker()
 		q.routineGroup.Run(func() {
diff --git a/queue_test.go b/queue_test.go
index 3affe42..0bd9232 100644
--- a/queue_test.go
+++ b/queue_test.go
@@ -24,7 +24,7 @@ func (m mockMessage) Bytes() []byte {
 	return []byte(m.message)
 }
 
-func TestNewQueue(t *testing.T) {
+func TestNewQueueWithZeroWorker(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
 
@@ -34,18 +34,44 @@ func TestNewQueue(t *testing.T) {
 
 	w := mocks.NewMockWorker(controller)
 	w.EXPECT().Shutdown().Return(nil)
-	w.EXPECT().Request().Return(nil, nil)
 	q, err = NewQueue(
 		WithWorker(w),
+		WithWorkerCount(0),
 	)
 	assert.NoError(t, err)
 	assert.NotNil(t, q)
 
 	q.Start()
+	time.Sleep(50 * time.Millisecond)
 	assert.Equal(t, 0, q.BusyWorkers())
 	q.Release()
 }
 
+func TestNewQueueWithDefaultWorker(t *testing.T) {
+	controller := gomock.NewController(t)
+	defer controller.Finish()
+
+	q, err := NewQueue()
+	assert.Error(t, err)
+	assert.Nil(t, q)
+
+	w := mocks.NewMockWorker(controller)
+	m := mocks.NewMockQueuedMessage(controller)
+	m.EXPECT().Bytes().Return([]byte("test")).AnyTimes()
+	w.EXPECT().Shutdown().Return(nil)
+	w.EXPECT().Request().Return(m, nil).AnyTimes()
+	w.EXPECT().Run(m).Return(nil).AnyTimes()
+	q, err = NewQueue(
+		WithWorker(w),
+	)
+	assert.NoError(t, err)
+	assert.NotNil(t, q)
+
+	q.Start()
+	q.Release()
+	assert.Equal(t, 0, q.BusyWorkers())
+}
+
 func TestShtdonwOnce(t *testing.T) {
 	w := &messageWorker{
 		messages: make(chan core.QueuedMessage, 100),
diff --git a/worker_test.go b/worker_test.go
index 47095bc..79d3c6a 100644
--- a/worker_test.go
+++ b/worker_test.go
@@ -3,6 +3,7 @@ package queue
 import (
 	"errors"
 	"testing"
+	"time"
 
 	"github.com/golang-queue/queue/core"
 	"github.com/golang-queue/queue/mocks"
@@ -30,5 +31,6 @@ func TestMockWorkerAndMessage(t *testing.T) {
 	assert.NoError(t, err)
 	assert.NotNil(t, q)
 	q.Start()
+	time.Sleep(50 * time.Millisecond)
 	q.Release()
 }