Go에서 중첩된 JSON을 객체 배열로 역마샬링하는 방법은 무엇입니까?

{
   "1001":{
      "level":10,
      "monster-id":1001,
      "skill-level":1,
      "aimer-id":301
   },
   "1002":{
      "level":12,
      "monster-id":1002,
      "skill-level":1,
      "aimer-id":302
   },
   "1003":{
      "level":16,
      "monster-id":1003,
      "skill-level":2,
      "aimer-id":303
   }
}

type Monster struct {
    MonsterId  int32
    Level      int32
    SkillLevel int32
    AimerId    int32
}

type MonsterCollection struct {
    Pool map[string]Monster
}

func (mc *MonsterCollection) FromJson(jsonStr string) error {
    var data *map[string]Monster
    b := []byte(jsonStr)
    return json.Unmarshal(b, &data)
}

type Monster struct {
    MonsterId  int32 `json:"monster-id"`
    Level      int32 `json:"level"`
    SkillLevel int32 `json:"skill-level"`
    AimerId    int32 `json:"aimer-id"`
}

mc := new(MonsterCollection)
err := mc.FromJson(jsonStr)

for id, monster := range mc.Pool {
    fmt.Println(id, monster)
}