如何将接口转换为自定义类型

package main

import "fmt"

type Animal interface {
    Sound() string
}

type Dog struct{}

func (d Dog) Sound() string {
    return "Woof!"
}

type Cat struct{}

func (c Cat) Sound() string {
    return "Meow!"
}

func main() {
    animals := []Animal{Dog{}, Cat{}}

    for _, animal := range animals {
        switch a := animal.(type) {
        case Dog:
            fmt.Println("This is a dog:", a.Sound())
        case Cat:
            fmt.Println("This is a cat:", a.Sound())
        default:
            fmt.Println("Unknown animal")
        }
    }
}

This is a dog: Woof!
This is a cat: Meow!