code: @Invalidate
      public void stop() throws InterruptedException {
          unregisterQuietly(vertxRegistration);
          unregisterQuietly(busRegistration);
          CountDownLatch latch = new CountDownLatch(1);
          vertx.close(v -> latch.countDown());
          latch.await();
          vertx = null;
      }
docs: Unregisters and shuts down the Vert.X singleton.