remove dead code

diff.go

diff --git a/diff.go b/diff.go
index 71e88de..5d7778a 100644
--- a/diff.go
+++ b/diff.go
@@ -113,11 +113,3 @@
 	}
 	return d1
 }
-
-
-func fieldLabel(label string, f reflect.StructField) string {
-	if label == "" {
-		return f.Name
-	}
-	return label + "." + f.Name
-}