diff --git a/examples/chatroom/main.go b/examples/chatroom/main.go
index 2eab51d0..ef00f904 100644
--- a/examples/chatroom/main.go
+++ b/examples/chatroom/main.go
@@ -23,8 +23,8 @@ func main() {
 	var upgrader = gws.NewUpgrader(handler, &gws.ServerOption{
 		PermessageDeflate: gws.PermessageDeflate{
 			Enabled:               true,
-			ServerContextTakeover: false,
-			ClientContextTakeover: false,
+			ServerContextTakeover: true,
+			ClientContextTakeover: true,
 		},
 
 		// 在querystring里面传入用户名
@@ -36,7 +36,7 @@ func main() {
 				return false
 			}
 			session.Store("name", name)
-			session.Store("key", r.Header.Get("Sec-WebSocket-Key"))
+			session.Store("websocketKey", r.Header.Get("Sec-WebSocket-Key"))
 			return true
 		},
 	})
@@ -59,42 +59,46 @@ func main() {
 	}
 }
 
+func MustLoad[T any](session gws.SessionStorage, key string) (v T) {
+	if value, exist := session.Load(key); exist {
+		v = value.(T)
+	}
+	return
+}
+
 func NewWebSocket() *WebSocket {
-	return &WebSocket{sessions: gws.NewConcurrentMap[string, *gws.Conn](16)}
+	return &WebSocket{
+		sessions: gws.NewConcurrentMap[string, *gws.Conn](16, 128),
+	}
 }
 
 type WebSocket struct {
 	sessions *gws.ConcurrentMap[string, *gws.Conn] // 使用内置的ConcurrentMap存储连接, 可以减少锁冲突
 }
 
-func (c *WebSocket) getName(socket *gws.Conn) string {
-	name, _ := socket.Session().Load("name")
-	return name.(string)
-}
-
-func (c *WebSocket) getKey(socket *gws.Conn) string {
-	name, _ := socket.Session().Load("key")
-	return name.(string)
-}
-
 func (c *WebSocket) OnOpen(socket *gws.Conn) {
-	name := c.getName(socket)
+	name := MustLoad[string](socket.Session(), "name")
 	if conn, ok := c.sessions.Load(name); ok {
-		conn.WriteClose(1000, []byte("connection replaced"))
+		conn.WriteClose(1000, []byte("connection is replaced"))
 	}
-	socket.SetDeadline(time.Now().Add(PingInterval + HeartbeatWaitTimeout))
+	_ = socket.SetDeadline(time.Now().Add(PingInterval + HeartbeatWaitTimeout))
 	c.sessions.Store(name, socket)
 	log.Printf("%s connected\n", name)
 }
 
 func (c *WebSocket) OnClose(socket *gws.Conn, err error) {
-	name := c.getName(socket)
-	key := c.getKey(socket)
-	if mSocket, ok := c.sessions.Load(name); ok {
-		if mKey := c.getKey(mSocket); mKey == key {
-			c.sessions.Delete(name)
+	name := MustLoad[string](socket.Session(), "name")
+	sharding := c.sessions.GetSharding(name)
+	sharding.Lock()
+	defer sharding.Unlock()
+
+	if conn, ok := sharding.Load(name); ok {
+		key0 := MustLoad[string](socket.Session(), "websocketKey")
+		if key1 := MustLoad[string](conn.Session(), "websocketKey"); key1 == key0 {
+			sharding.Delete(name)
 		}
 	}
+
 	log.Printf("onerror, name=%s, msg=%s\n", name, err.Error())
 }
 
@@ -114,14 +118,14 @@ func (c *WebSocket) OnMessage(socket *gws.Conn, message *gws.Message) {
 	defer message.Close()
 
 	// chrome websocket不支持ping方法, 所以在text frame里面模拟ping
-	if b := message.Data.Bytes(); len(b) == 4 && string(b) == "ping" {
+	if b := message.Bytes(); len(b) == 4 && string(b) == "ping" {
 		c.OnPing(socket, nil)
 		return
 	}
 
 	var input = &Input{}
-	_ = json.Unmarshal(message.Data.Bytes(), input)
+	_ = json.Unmarshal(message.Bytes(), input)
 	if conn, ok := c.sessions.Load(input.To); ok {
-		conn.WriteMessage(gws.OpcodeText, message.Data.Bytes())
+		_ = conn.WriteMessage(gws.OpcodeText, message.Bytes())
 	}
 }
diff --git a/session_storage.go b/session_storage.go
index f7acaa5e..94999bde 100644
--- a/session_storage.go
+++ b/session_storage.go
@@ -62,78 +62,114 @@ type (
 	ConcurrentMap[K comparable, V any] struct {
 		hasher   maphash.Hasher[K]
 		sharding uint64
-		buckets  []*bucket[K, V]
-	}
-
-	bucket[K comparable, V any] struct {
-		sync.Mutex
-		m map[K]V
+		buckets  []*Map[K, V]
 	}
 )
 
-func NewConcurrentMap[K comparable, V any](sharding uint64) *ConcurrentMap[K, V] {
-	sharding = internal.SelectValue(sharding == 0, 16, sharding)
+// NewConcurrentMap create a new concurrency-safe map
+// arg0 represents the number of shardings; arg1 represents the initialized capacity of a sharding.
+func NewConcurrentMap[K comparable, V any](size ...uint64) *ConcurrentMap[K, V] {
+	sharding, capacity := uint64(16), uint64(0)
+	if len(size) >= 1 {
+		sharding = size[0]
+	}
+	if len(size) >= 2 {
+		capacity = size[1]
+	}
+	sharding = internal.SelectValue(sharding <= 0, 16, sharding)
 	sharding = internal.ToBinaryNumber(sharding)
 	var cm = &ConcurrentMap[K, V]{
 		hasher:   maphash.NewHasher[K](),
 		sharding: sharding,
-		buckets:  make([]*bucket[K, V], sharding),
+		buckets:  make([]*Map[K, V], sharding),
 	}
 	for i, _ := range cm.buckets {
-		cm.buckets[i] = &bucket[K, V]{m: make(map[K]V)}
+		cm.buckets[i] = &Map[K, V]{m: make(map[K]V, capacity)}
 	}
 	return cm
 }
 
-func (c *ConcurrentMap[K, V]) getBucket(key K) *bucket[K, V] {
+// GetSharding returns a map sharding for a key
+func (c *ConcurrentMap[K, V]) GetSharding(key K) *Map[K, V] {
 	var hashCode = c.hasher.Hash(key)
 	var index = hashCode & (c.sharding - 1)
 	return c.buckets[index]
 }
 
+// Len returns the number of elements in the map
 func (c *ConcurrentMap[K, V]) Len() int {
 	var length = 0
 	for _, b := range c.buckets {
 		b.Lock()
-		length += len(b.m)
+		length += b.Len()
 		b.Unlock()
 	}
 	return length
 }
 
-func (c *ConcurrentMap[K, V]) Load(key K) (value V, exist bool) {
-	var b = c.getBucket(key)
+// Load returns the value stored in the map for a key, or nil if no
+// value is present.
+// The ok result indicates whether value was found in the map.
+func (c *ConcurrentMap[K, V]) Load(key K) (value V, ok bool) {
+	var b = c.GetSharding(key)
 	b.Lock()
-	value, exist = b.m[key]
+	value, ok = b.Load(key)
 	b.Unlock()
 	return
 }
 
+// Delete deletes the value for a key.
 func (c *ConcurrentMap[K, V]) Delete(key K) {
-	var b = c.getBucket(key)
+	var b = c.GetSharding(key)
 	b.Lock()
-	delete(b.m, key)
+	b.Delete(key)
 	b.Unlock()
 }
 
+// Store sets the value for a key.
 func (c *ConcurrentMap[K, V]) Store(key K, value V) {
-	var b = c.getBucket(key)
+	var b = c.GetSharding(key)
 	b.Lock()
-	b.m[key] = value
+	b.Store(key, value)
 	b.Unlock()
 }
 
 // Range calls f sequentially for each key and value present in the map.
 // If f returns false, range stops the iteration.
 func (c *ConcurrentMap[K, V]) Range(f func(key K, value V) bool) {
-	for _, b := range c.buckets {
+	var next = true
+	var cb = func(k K, v V) bool {
+		next = f(k, v)
+		return next
+	}
+	for i := uint64(0); i < c.sharding && next; i++ {
+		var b = c.buckets[i]
 		b.Lock()
-		for k, v := range b.m {
-			if !f(k, v) {
-				b.Unlock()
-				return
-			}
-		}
+		b.Range(cb)
 		b.Unlock()
 	}
 }
+
+type Map[K comparable, V any] struct {
+	sync.Mutex
+	m map[K]V
+}
+
+func (c *Map[K, V]) Len() int { return len(c.m) }
+
+func (c *Map[K, V]) Load(key K) (value V, ok bool) {
+	value, ok = c.m[key]
+	return
+}
+
+func (c *Map[K, V]) Delete(key K) { delete(c.m, key) }
+
+func (c *Map[K, V]) Store(key K, value V) { c.m[key] = value }
+
+func (c *Map[K, V]) Range(f func(K, V) bool) {
+	for k, v := range c.m {
+		if !f(k, v) {
+			return
+		}
+	}
+}
diff --git a/session_storage_test.go b/session_storage_test.go
index 3b215f07..8a6e66d7 100644
--- a/session_storage_test.go
+++ b/session_storage_test.go
@@ -123,6 +123,15 @@ func TestConcurrentMap(t *testing.T) {
 		as.Equal(v, v1)
 	}
 	as.Equal(len(m1), m2.Len())
+
+	t.Run("", func(t *testing.T) {
+		var sum = 0
+		var cm = NewConcurrentMap[string, int](8, 8)
+		for _, item := range cm.buckets {
+			sum += len(item.m)
+		}
+		assert.Equal(t, sum, 0)
+	})
 }
 
 func TestConcurrentMap_Range(t *testing.T) {