diff --git a/core/nat.go b/core/nat.go
index 6a57a26..223be38 100644
--- a/core/nat.go
+++ b/core/nat.go
@@ -7,7 +7,6 @@ import (
 	"net"
 	"strconv"
 	"strings"
-	"sync"
 	"time"
 
 	reuse "github.com/openp2p-cn/go-reuseport"