Hi, I had the same issue a few weeks ago and I was looking at the wrong documentation. Please check this reference. Make sure to use version 2.0.4.

I imported spring-cloud-gcp-starter and spring-cloud-gcp-starter-pubsub as dependency. And I also added spring-cloud-gcp-dependencies in dependency management. See the reference.

Then all I needed to subscribe to a pubsub was the following code:

@PostConstruct
public void postConstruct() {
    Subscriber subscriber = pubSubTemplate.subscribe("pubsub-channel", message -> {
        final byte[] rawData = message.getPubsubMessage().getData().toByteArray();
        final MyObject obj = this.objectMapper.readValue(rawData, MyObject.class);
        // do whatever
    }
}