in src/main/java/com/spotify/google/cloud/pubsub/client/Publisher.java [191:201]
public void close() {
// TODO (dano): fail outstanding futures
scheduler.shutdownNow();
try {
scheduler.awaitTermination(30, SECONDS);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
closeFuture.complete(null);
listener.publisherClosed(Publisher.this);
}