Go에서 상위 유형 객체의 하위 유형 속성에 액세스하는 방법은 무엇입니까?

<code>package main

import (
    "fmt"
    "time"
)

type File interface{}

type Audio struct {
    File
    Duration time.Duration
}

type Image struct {
    File
    Width  uint
    Height uint
}

func main() {
    var files = map[string]File{
        "1": Audio{
            Duration: 14 * time.Second,
        },
        "2": Image{
            Height: 9989,
            Width:  1111,
        },
        "3": Image{
                        Width:  1234,
            Height: 5678,
        },
    }
    for k, v := range files {
        switch v.(type) {
        case Audio:
            fmt.Printf("%s: Audio %d seconds", k, v.Duration / time.Second)
        case Image:
            fmt.Printf("%s: Image %dx%d", k, v.Width, v.Height)
        }
    }
}
</code>