fix

diffmatchpatch/diff.go

diff --git a/diffmatchpatch/diff.go b/diffmatchpatch/diff.go
index f70d6f3..16b03f2 100644
--- a/diffmatchpatch/diff.go
+++ b/diffmatchpatch/diff.go
@@ -500,8 +500,8 @@
 // DiffCommonOverlap determines if the suffix of one string is the prefix of another.
 func (dmp *DiffMatchPatch) DiffCommonOverlap(text1 string, text2 string) int {
 	// Cache the text lengths to prevent multiple calls.
-	text1Length := len(text1)
-	text2Length := len(text2)
+	text1Length := len([]rune(text1))
+	text2Length := len([]rune(text2))
 	// Eliminate the null case.
 	if text1Length == 0 || text2Length == 0 {
 		return 0

diffmatchpatch/diff_test.go

diff --git a/diffmatchpatch/diff_test.go b/diffmatchpatch/diff_test.go
index 6c159cb..e3689ae 100644
--- a/diffmatchpatch/diff_test.go
+++ b/diffmatchpatch/diff_test.go
@@ -845,6 +845,18 @@
 				{DiffInsert, "a new hope"},
 			},
 		},
+		{
+			"panic",
+			[]Diff{
+				{DiffInsert, "킬러 인 "},
+				{DiffEqual, "리커버리"},
+				{DiffDelete, " 보이즈"},
+			},
+			[]Diff{
+				{DiffDelete, "리커버리 보이즈"},
+				{DiffInsert, "킬러 인 리커버리"},
+			},
+		},
 	} {
 		actual := dmp.DiffCleanupSemantic(tc.Diffs)
 		assert.Equal(t, tc.Expected, actual, fmt.Sprintf("Test case #%d, %s", i, tc.Name))