only print diff in example_test if test.v is set

generate/example_test.go

@@ -61,6 +61,9 @@ func TestRunExample(t *testing.T) {
 	got := strings.TrimSpace(string(out))
 	want := "benjaminjkraft is Ben Kraft created on 2009-08-03"
 	if got != want {
-		t.Errorf("output incorrect\ngot:\n%s\nwant:\n%s", got, want)
+		t.Errorf("output incorrect")
+		if testing.Verbose() {
+			t.Errorf("got:\n%s\nwant:\n%s", got, want)
+		}
 	}
 }