diff --git a/session_storage.go b/session_storage.go
index bc2cbedf..0b09c184 100644
--- a/session_storage.go
+++ b/session_storage.go
@@ -60,46 +60,41 @@ func (c *smap) Range(f func(key string, value any) bool) {
 
 type (
 	ConcurrentMap[K comparable, V any] struct {
-		hasher   maphash.Hasher[K]
-		sharding uint64
-		buckets  []*Map[K, V]
+		hasher    maphash.Hasher[K]
+		num       uint64
+		shardings []*Map[K, V]
 	}
 )
 
 // 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(0), 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)
+	size = append(size, 0, 0)
+	num, capacity := size[0], size[1]
+	num = internal.ToBinaryNumber(internal.SelectValue(num <= 0, 16, num))
 	var cm = &ConcurrentMap[K, V]{
-		hasher:   maphash.NewHasher[K](),
-		sharding: sharding,
-		buckets:  make([]*Map[K, V], sharding),
+		hasher:    maphash.NewHasher[K](),
+		num:       num,
+		shardings: make([]*Map[K, V], num),
 	}
-	for i, _ := range cm.buckets {
-		cm.buckets[i] = &Map[K, V]{m: make(map[K]V, capacity)}
+	for i, _ := range cm.shardings {
+		cm.shardings[i] = NewMap[K, V](int(capacity))
 	}
 	return cm
 }
 
 // GetSharding returns a map sharding for a key
+// the operations inside the sharding is lockless, and need to be locked manually.
 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]
+	var index = hashCode & (c.num - 1)
+	return c.shardings[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 {
+	for _, b := range c.shardings {
 		b.Lock()
 		length += b.Len()
 		b.Unlock()
@@ -142,8 +137,8 @@ func (c *ConcurrentMap[K, V]) Range(f func(key K, value V) bool) {
 		next = f(k, v)
 		return next
 	}
-	for i := uint64(0); i < c.sharding && next; i++ {
-		var b = c.buckets[i]
+	for i := uint64(0); i < c.num && next; i++ {
+		var b = c.shardings[i]
 		b.Lock()
 		b.Range(cb)
 		b.Unlock()
@@ -155,6 +150,16 @@ type Map[K comparable, V any] struct {
 	m map[K]V
 }
 
+func NewMap[K comparable, V any](size ...int) *Map[K, V] {
+	var capacity = 0
+	if len(size) > 0 {
+		capacity = size[0]
+	}
+	c := new(Map[K, V])
+	c.m = make(map[K]V, capacity)
+	return c
+}
+
 func (c *Map[K, V]) Len() int { return len(c.m) }
 
 func (c *Map[K, V]) Load(key K) (value V, ok bool) {
diff --git a/session_storage_test.go b/session_storage_test.go
index 883230e9..d4c8b5e5 100644
--- a/session_storage_test.go
+++ b/session_storage_test.go
@@ -100,7 +100,7 @@ func TestConcurrentMap(t *testing.T) {
 	var as = assert.New(t)
 	var m1 = make(map[string]any)
 	var m2 = NewConcurrentMap[string, uint32]()
-	as.Equal(m2.sharding, uint64(16))
+	as.Equal(m2.num, uint64(16))
 	var count = internal.AlphabetNumeric.Intn(1000)
 	for i := 0; i < count; i++ {
 		var key = string(internal.AlphabetNumeric.Generate(10))
@@ -128,7 +128,7 @@ func TestConcurrentMap(t *testing.T) {
 	t.Run("", func(t *testing.T) {
 		var sum = 0
 		var cm = NewConcurrentMap[string, int](8, 8)
-		for _, item := range cm.buckets {
+		for _, item := range cm.shardings {
 			sum += len(item.m)
 		}
 		assert.Equal(t, sum, 0)