如何在switch中对多个type进行匹配

比如， case int, float64 编译会报错，有没有什么方法能实现这种用法呢？

package main

import "fmt"

func do(i interface{}) {
    switch v := i.(type) {
    case int, float64: // Illegal! Then how?
        fmt.Printf("Twice %v is %v\n", v, v*2)
    case string:
        fmt.Printf("%q is %v bytes long\n", v, len(v))
    default:
        fmt.Printf("I don't know about type %T!\n", v)
    }
}

func main() {
    do(21)
    do(3.13)
    do("hello")
    do(true)
}