问题：为何我请求了用户详细信息，用户openid ：o3vH-jilxd-CC-GOK9a2rpZjnvOk ，为何没有返回unionid这个字段，我理解是只要这个用户关注我的公众号，肯定会有该字段
 才对呀？

https://developers.weixin.qq.com/doc/offiaccount/User_Management/Get_users_basic_information_UnionID.html#UinonId

请求参数：https://api.weixin.qq.com/cgi-bin/user/info?access_token=44_CDUZgkbaJKlECkmKJn-50xQVgrmX_NAEsGkkl-p3TZnUEU09kiI5Cop9IYB2ESvw02dlfRrSnE4DEDWGKhbS7zSMLUn36R656coS2dQ_f37uYonhGodso6_Q0JKCcxQSqt8an5MrOXNeCHFXJOKaAEAPUQ&openid=o3vH-jilxd-CC-GOK9a2rpZjnvOk&lang=zh_CN

返回参数：{

    "subscribe": 1,

    "openid": "o3vH-jilxd-CC-GOK9a2rpZjnvOk",

    "nickname": "Seven",

    "sex": 1,

    "language": "zh_CN",

    "city": "",

    "province": "都灵",

    "country": "意大利",

    "headimgurl": "http://thirdwx.qlogo.cn/mmopen/TlrKkMFJVwUFSHrv7nfuLSztC6lt5TZIJKZ2sKBQhMSNA15EicmphVNhJhNImes88M4cODlg6aWZictbaicOKKAR2ok58fzk3xr/132",

    "subscribe_time": 1465872747,

    "remark": "",

    "groupid": 0,

    "tagid_list": [],

    "subscribe_scene": "ADD_SCENE_OTHERS",

    "qr_scene": 0,

    "qr_scene_str": ""

}