1.用户点击某按钮时才能调用，方法：

   var _this = this;
        wx.requestSubscribeMessage({
            tmplIds: ['IfU3eOcH_ubviSy5EqYJkGpN_i1-w_JsUHCyZTTybS0'],
            success (res) { 
                console.log(res);
                _this.message();
            }
        })

需要推送消息的时候 调服务端接口

  message() {
    var that = this;
    //订阅消息模板id
    var template_id ="IfU3eOcH_ubviSy5EqYJkGpN_i1-w_JsUHCyZTTybS0";
   
      //发送access_token请求
      console.log(app.globalData.userInfo.openId);
      var test = {
            access_token: '50_iVSlpAnvMouQeEs14oAo-rL2vrBTFWblzuhXGrAvP8NMvyiC2BHzql3NU-LwB1KnbiDtH616M3ymenO4bMd9bH2IFhc2pPdRgvxS1OVzrx9fd4-QRlN9llhbGGpRjXAozB1ho_oQMaVJm0HLQKNfAHAJDG',
            data:{
              "touser": app.globalData.userInfo.openId,
              "template_id": template_id,
              "page": "pages/index/index",
              "miniprogram_state": "trial",
              "lang": "zh_CN",
              "data": {
                
                thing2: {value:"11111"},
                thing5: {value: "订单已送达"},
                character_string6: {value: "SF4420210302"},
                
              }
            }
          }
        wx.request({
          url: 'http://192.168.210.10:3000/list',
          method: 'post',
          data: test,
          success: function(res) {
            console.log("订阅成功");
            console.log(res);
          },
          fail: function(res) {
            console.log("订阅失败");
          },
        })

  },

服务端接口中 调用微信提供的api
我用nodejs写的

app.post('/list', (req, res) => {
    console.log('---',req);
        console.log("%s", "guoyansi", req.body.access_token);
        request({
            url: 'https://api.weixin.qq.com/cgi-bin/message/subscribe/send?access_token='+req.body.access_token,
            method: "POST",
            json: true,
            headers: {
                "content-type": "application/json",
            },
            body: req.body.data
        }, function(error, response, body) {
            if (!error && response.statusCode == 200) {
                res.json({
                    code: 200,
                    message: '成功',
                    data: {
                      list: body
                    }
                  });
            }
        }); 


})