Can't enable PubSub feature for ephemeral temporary node

I’m trying to adopt this example to my needs and current state of libraries:

I’m able to start temporary node and some basic activity but I can’t use pubsub feature.
It is enabled in config with cfg.Pubsub.Enabled=1:

	// Create a config with default options and a 2048 bit key
	cfg, err := config.Init(ioutil.Discard, 2048)
	if err != nil {
		return "", err
	// Create the repo with the config
	err = fsrepo.Init(repoPath, cfg)
	if err != nil {
		return "", fmt.Errorf("failed to init ephemeral node: %s", err)

But it is impossible to use. Code like

func topic_sub(ctx context.Context, chnl chan string, ipfs icore.CoreAPI, topic string) {
	subscription, err := ipfs.PubSub().Subscribe(ctx, topic)

returns “Error! Failed topic subscribtion in topic_subexperimental pubsub feature not enabled. Run daemon with --enable-pubsub-experiment to use.” And it points out that pubsub is not enabled actually.
Any ideas how to make it work?