docs: public void close() {
          SHUTDOWN_EXECUTOR.execute(new Runnable() {
              
              @Override
              public void run() {
                  try {
                      executorService.shutdown();
                      while (!executorService.awaitTermination(5, TimeUnit.SECONDS)) {
                          executorService.shutdownNow();
                      }
                  } catch (final InterruptedException ex) {
                      Thread.currentThread().interrupt();
                  }
              }
          });
      }