code: protected void unregister() {
          if (providerConfig.isRegister()) {
              List<RegistryConfig> registryConfigs = providerConfig.getRegistry();
              if (registryConfigs != null) {
                  for (RegistryConfig registryConfig : registryConfigs) {
                      Registry registry = RegistryFactory.getRegistry(registryConfig);
                      try {
                          registry.unRegister(providerConfig);
                      } catch (Exception e) {
                          String appName = providerConfig.getAppName();
                          if (LOGGER.isWarnEnabled(appName)) {
                              LOGGER.warnWithApp(appName, "Catch exception when unRegister from registry: " +
                                  registryConfig.getId()
                                  + ", but you can ignore if it's called by JVM shutdown hook", e);
                          }
                      }
                  }
              }
          }
      }
docs: 反注册服务