fix stringutil tests

Change-Id: Ie6ad5645ac6fca6af22376f2fda00e1c4772ae19
diff --git a/stringutil/reverse_test.go b/stringutil/reverse_test.go
index 263a420..3a2337f 100644
--- a/stringutil/reverse_test.go
+++ b/stringutil/reverse_test.go
@@ -19,7 +19,7 @@
 import "testing"
 
 func TestReverse(t *testing.T) {
-	for _, c := range struct {
+	for _, c := range []struct {
 		in, want string
 	}{
 		{"Hello, world", "dlrow ,olleH"},
@@ -27,8 +27,8 @@
 		{"", ""},
 	} {
 		got := Reverse(c.in)
-		if got != want {
-			t.Errorf("Reverse(%q) == %q, want %q", c.in, got, want)
+		if got != c.want {
+			t.Errorf("Reverse(%q) == %q, want %q", c.in, got, c.want)
 		}
 	}
 }