code: @Beta(SinceVersion.V1_1_0)
      public void close() {
          httpClient.dispatcher().executorService().shutdown();
          httpClient.connectionPool().evictAll();
          synchronized (httpClient.connectionPool()) {
              httpClient.connectionPool().notifyAll();
          }
          synchronized (AsyncTimeout.class) {
              AsyncTimeout.class.notifyAll();
          }
      }
docs: Closes the HTTP client and recycles the resources associated. The threads will
  be recycled after 60 seconds of inactivity.