package main

import (
    "fmt"
    "io"
)

type fu int

func (fu) Bar() {}

type barer interface {
    Bar()
}

func main() {
    var i interface{} = fu(1)
    switch i.(type) {
    case io.Reader:
        fmt.Println("reader")
    case int:
        fmt.Println("int")
    case barer:
        fmt.Println("barer")
    case fu:
        fmt.Println("fu")
    }
}