public static <T> T getExtension(Class<T> clazz, boolean isSingleton) {
    List<T> extensionList = getExtensionList(clazz);
    if (extensionList == null || extensionList.isEmpty()) {
      return null;
    }
    return extensionList.get(0);
  }
Get extension class with highest {@link Order} value.
src/main/java/com/eudemon/ratelimiter/extension/ExtensionLoader.java