docs: public void unregister(GracefulShutdownHook shutdownHook) {
          if (isShuttingDown.get()) {
              // Avoid any changes to the shutdown hooks set when the shutdown is already in progress
              throw new IllegalStateException("Couldn't unregister shutdown hook because shutdown is already in progress");
          }
          shutdownHooks.remove(requireNonNull(shutdownHook, "shutdownHook cannot be null"));
      }