json串解析问题

大神帮忙看看我这个程序的问题出在哪里了？总是差一些解析不出来正确的结果。

package main

import (
    "encoding/json"
    "fmt"
)

type hisData struct {
    Ms    string `json:"Ms"`
    Time  string `json:"Time"`
    Value string `json:"Value"`
}

func main() {
    str := `{
  "SF2WT.x1_zjs_sfc_ps20kt_4-5_100-1239_pv:1": [
    {
      "Ms": 0,
      "Value": "0",
      "Time": "2019/11/28 10:00:21.000"
    },
    {
      "Ms": 0,
      "Value": "68.75",
      "Time": "2019/11/28 10:00:59.000"
    },
    {
      "Ms": 0,
      "Value": "39.375",
      "Time": "2019/11/28 10:01:01.000"
    }
  ],
  "SF2WT.x1_zjs_sfc_ps20kt_4-5_100-1239_sum:1": [
    {
      "Ms": 0,
      "Value": "14.6875",
      "Time": "2019/11/28 10:01:03.000"
    },
    {
      "Ms": 0,
      "Value": "9.0625",
      "Time": "2019/11/28 10:01:05.000"
    },
    {
      "Ms": 0,
      "Value": "6.25",
      "Time": "2019/11/28 10:01:07.000"
    },
    {
      "Ms": 0,
      "Value": "12.5",
      "Time": "2019/11/28 10:01:09.000"
    }
  ]
}`
    type mp map[string][]hisData
    var v mp
    json.Unmarshal([]byte(str), &v)

    fmt.Println(fmt.Sprintf("%+v", v))
}

运行后的结果是： map[SF2WT.x1_zjs_sfc_ps20kt_4-5_100-1239_pv:1:[{Ms: Time:2019/11/28 10:00:21.000 Value:0} {Ms: Time:2019/11/28 10:00:59.000 Value:68.75} {Ms: Time:2019/11/28 10:01:01.000 Value:39.375}] SF2WT.x1_zjs_sfc_ps20kt_4-5_100-1239_sum:1:[{Ms: Time:2019/11/28 10:01:03.000 Value:14.6875} {Ms: Time:2019/11/28 10:01:05.000 Value:9.0625} {Ms: Time:2019/11/28 10:01:07.000 Value:6.25} {Ms: Time:2019/11/28 10:01:09.000 Value:12.5}]]