code: public GetUsersResponse getUsersByTagId(Integer tagId, String nextOpenid) {
          BeanUtil.requireNonNull(tagId, "tagId is null");
          GetUsersResponse response;
          LOG.debug("开始获取标签下粉丝.....");
          String url = BASE_API_URL + "cgi-bin/user/tag/get?access_token=#";
          Map<String, Object> param = new HashMap<String, Object>();
          param.put("tagid", tagId);
          param.put("next_openid", null == nextOpenid ? "" : nextOpenid);
          BaseResponse r = executePost(url, JSONUtil.toJson(param));
          String resultJson = isSuccess(r.getErrcode()) ? r.getErrmsg() : r.toJsonString();
          response = JSONUtil.toBean(resultJson, GetUsersResponse.class);
          return response;
      }
docs: 获取标签下粉丝
  @param tagId 标签ID
  @param nextOpenid 下一个用户的openid,第一次不用填
  @return 本批用户列表