diff --git a/cmd/Open-IM-SDK-Core b/cmd/Open-IM-SDK-Core
index 2257ac8ee..9d67999ce 160000
--- a/cmd/Open-IM-SDK-Core
+++ b/cmd/Open-IM-SDK-Core
@@ -1 +1 @@
-Subproject commit 2257ac8ee528fb1e0038f85e34c8770fbe4758e3
+Subproject commit 9d67999cec3e4a9792c33a95e5514a945df54052
diff --git a/pkg/utils/utils.go b/pkg/utils/utils.go
index d23b1633a..8f0b52d72 100644
--- a/pkg/utils/utils.go
+++ b/pkg/utils/utils.go
@@ -39,6 +39,8 @@ func cleanUpFuncName(funcName string) string {
 	}
 	return funcName[end+1:]
 }
+
+//Get the intersection of two slices
 func Intersect(slice1, slice2 []uint32) []uint32 {
 	m := make(map[uint32]bool)
 	n := make([]uint32, 0)
@@ -53,6 +55,8 @@ func Intersect(slice1, slice2 []uint32) []uint32 {
 	}
 	return n
 }
+
+//Get the diff of two slices
 func Difference(slice1, slice2 []uint32) []uint32 {
 	m := make(map[uint32]bool)
 	n := make([]uint32, 0)