Go 구조체에서 임의의 JSON 키를 처리하는 방법은 무엇입니까?

type Items map[string][]ImageUrl

type ImageUrl struct {
    Url string
    Width, Height int
}

type Items map[string][]ImageUrl

func main() {
    json := `{"items":
[{"name": "thing",
  "image_urls": {
    "50x100": [{
      "url": "http://site.com/images/1/50x100.jpg",
      "width": 50,
      "height": 100
    }, {
      "url": "http://site.com/images/2/50x100.jpg",
      "width": 50,
      "height": 100
    }],
    "200x300": [{
      "url": "http://site.com/images/1/200x300.jpg",
      "width": 200,
      "height": 300
    }],
    "400x520": [{
      "url": "http://site.com/images/1/400x520.jpg",
      "width": 400,
      "height": 520
    }]
  }
}
}`

    var items Items
    if err := json.Unmarshal([]byte(json), &items); err != nil {
        // Handle error
    }

    fmt.Println(items) // Prints the map containing the keys and values
}