iter, err := tf.QueryJSON(context.Background())
if err != nil {
	t.Fatalf("error running Query: %s", err)
}

for nextMsg := range iter {
	if nextMsg.Err != nil {
		// handle error
		break
	}
	switch m := nextMsg.Msg.(type) {
	case tfjson.ListStartMessage:
		// do something
	case tfjson.ListResourceFoundMessage:
		// do something
	case tfjson.ListCompleteMessage:
		// do something
	}
}