code: public static synchronized void releaseSharedResources() {
          if (SHARED_EVENT_LOOP != null) {
              SHARED_EVENT_LOOP.shutdownGracefully();
              SHARED_EVENT_LOOP = null;
          }
          if (SHARED_WHEEL_TIMER != null) {
              SHARED_WHEEL_TIMER.stop();
              SHARED_WHEEL_TIMER = null;
          }
          if (SHARED_EXECUTOR != null) {
              SHARED_EXECUTOR.shutdown();
              SHARED_EXECUTOR = null;
          }
          if (SHARED_SCHEDULED_EXECUTOR != null) {
              SHARED_SCHEDULED_EXECUTOR.shutdown();
              SHARED_SCHEDULED_EXECUTOR = null;
          }
      }
docs: Release/shutdown/cleanup any shared resources that were created.