diff --git a/datastruct/dict/concurrent.go b/datastruct/dict/concurrent.go
index 2ece9cd6..217143bf 100644
--- a/datastruct/dict/concurrent.go
+++ b/datastruct/dict/concurrent.go
@@ -185,7 +185,7 @@ func (dict *ConcurrentDict) PutIfAbsentWithLock(key string, val interface{}) (re
 	return 1
 }
 
-// PutIfExists puts value if the key is exist and returns the number of inserted key-value
+// PutIfExists puts value if the key is existed and returns the number of inserted key-value
 func (dict *ConcurrentDict) PutIfExists(key string, val interface{}) (result int) {
 	if dict == nil {
 		panic("dict is nil")
@@ -262,7 +262,7 @@ func (dict *ConcurrentDict) decreaseCount() int32 {
 }
 
 // ForEach traversal the dict
-// it may not visits new entry inserted during traversal
+// it may not visit new entry inserted during traversal
 func (dict *ConcurrentDict) ForEach(consumer Consumer) {
 	if dict == nil {
 		panic("dict is nil")
diff --git a/datastruct/dict/simple.go b/datastruct/dict/simple.go
index 61839656..49be8f33 100644
--- a/datastruct/dict/simple.go
+++ b/datastruct/dict/simple.go
@@ -46,7 +46,7 @@ func (dict *SimpleDict) PutIfAbsent(key string, val interface{}) (result int) {
 	return 1
 }
 
-// PutIfExists puts value if the key is exist and returns the number of inserted key-value
+// PutIfExists puts value if the key is existed and returns the number of inserted key-value
 func (dict *SimpleDict) PutIfExists(key string, val interface{}) (result int) {
 	_, existed := dict.m[key]
 	if existed {
diff --git a/datastruct/lock/lock_map.go b/datastruct/lock/lock_map.go
index e4bb4ef5..72fd0963 100644
--- a/datastruct/lock/lock_map.go
+++ b/datastruct/lock/lock_map.go
@@ -39,7 +39,7 @@ func (locks *Locks) spread(hashCode uint32) uint32 {
 		panic("dict is nil")
 	}
 	tableSize := uint32(len(locks.table))
-	return (tableSize - 1) & uint32(hashCode)
+	return (tableSize - 1) & hashCode
 }
 
 // Lock obtains exclusive lock for writing
@@ -90,7 +90,7 @@ func (locks *Locks) toLockIndices(keys []string, reverse bool) []uint32 {
 }
 
 // Locks obtains multiple exclusive locks for writing
-// invoking Lock in loop may cause dead lock, please use Locks
+// invoking Lock in loop may cause deadlock, please use Locks
 func (locks *Locks) Locks(keys ...string) {
 	indices := locks.toLockIndices(keys, false)
 	for _, index := range indices {
@@ -100,7 +100,7 @@ func (locks *Locks) Locks(keys ...string) {
 }
 
 // RLocks obtains multiple shared locks for reading
-// invoking RLock in loop may cause dead lock, please use RLocks
+// invoking RLock in loop may cause deadlock, please use RLocks
 func (locks *Locks) RLocks(keys ...string) {
 	indices := locks.toLockIndices(keys, false)
 	for _, index := range indices {
diff --git a/datastruct/sortedset/sortedset.go b/datastruct/sortedset/sortedset.go
index 67f7942d..52eacf3a 100644
--- a/datastruct/sortedset/sortedset.go
+++ b/datastruct/sortedset/sortedset.go
@@ -78,7 +78,7 @@ func (sortedSet *SortedSet) GetRank(member string, desc bool) (rank int64) {
 
 // ForEachByRank visits each member which rank within [start, stop), sort by ascending order, rank starts from 0
 func (sortedSet *SortedSet) ForEachByRank(start int64, stop int64, desc bool, consumer func(element *Element) bool) {
-	size := int64(sortedSet.Len())
+	size := sortedSet.Len()
 	if start < 0 || start >= size {
 		panic("illegal start " + strconv.FormatInt(start, 10))
 	}
@@ -91,12 +91,12 @@ func (sortedSet *SortedSet) ForEachByRank(start int64, stop int64, desc bool, co
 	if desc {
 		node = sortedSet.skiplist.tail
 		if start > 0 {
-			node = sortedSet.skiplist.getByRank(int64(size - start))
+			node = sortedSet.skiplist.getByRank(size - start)
 		}
 	} else {
 		node = sortedSet.skiplist.header.level[0].forward
 		if start > 0 {
-			node = sortedSet.skiplist.getByRank(int64(start + 1))
+			node = sortedSet.skiplist.getByRank(start + 1)
 		}
 	}
 
diff --git a/tcp/echo_test.go b/tcp/echo_test.go
index 1bc211c8..ef2bd5cc 100644
--- a/tcp/echo_test.go
+++ b/tcp/echo_test.go
@@ -51,3 +51,38 @@ func TestListenAndServe(t *testing.T) {
 	closeChan <- struct{}{}
 	time.Sleep(time.Second)
 }
+
+func TestClientCounter(t *testing.T) {
+	var err error
+	closeChan := make(chan struct{})
+	listener, err := net.Listen("tcp", ":0")
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	addr := listener.Addr().String()
+	go ListenAndServe(listener, MakeEchoHandler(), closeChan)
+
+	sleepUntil := time.Now().Add(3 * time.Second)
+	subtime := func() time.Duration {
+		return sleepUntil.Sub(time.Now())
+	}
+
+	for i := 0; i < 1000; i++ {
+		go func() {
+			conn, err := net.Dial("tcp", addr)
+			if err != nil {
+				t.Errorf(err.Error())
+			}
+			defer conn.Close()
+
+			time.Sleep(subtime())
+		}()
+		time.Sleep(5 * time.Microsecond)
+	}
+
+	time.Sleep(3 * time.Second)
+	if ClientCounter != 0 {
+		t.Errorf("client counter error: %d", ClientCounter)
+	}
+}
diff --git a/tcp/server.go b/tcp/server.go
index e381de17..b74de25d 100644
--- a/tcp/server.go
+++ b/tcp/server.go
@@ -11,6 +11,7 @@ import (
 	"os"
 	"os/signal"
 	"sync"
+	"sync/atomic"
 	"syscall"
 	"time"
 
@@ -26,7 +27,7 @@ type Config struct {
 }
 
 // ClientCounter Record the number of clients in the current Godis server
-var ClientCounter int
+var ClientCounter int32
 
 // ListenAndServeWithSignal binds port and handle requests, blocking until receive stop signal
 func ListenAndServeWithSignal(cfg *Config, handler tcp.Handler) error {
@@ -88,7 +89,7 @@ func ListenAndServe(listener net.Listener, handler tcp.Handler, closeChan <-chan
 		go func() {
 			defer func() {
 				waitDone.Done()
-				ClientCounter--
+				atomic.AddInt32(&ClientCounter, -1)
 			}()
 			handler.Handle(ctx, conn)
 		}()