package main
 
import "fmt"
 
func describe(i interface{}) {
    switch v := i.(type) {
    case nil:
        fmt.Println("nil value")
    case int:
        fmt.Printf("int: %d\n", v)
    case string:
        fmt.Printf("string: %s\n", v)
    case []int:
        fmt.Printf("int slice with %d elements\n", len(v))
    default:
        fmt.Printf("unknown type: %T\n", v)
    }
}
 
func main() {
    describe(42)
    describe("hello")
    describe([]int{1, 2, 3})
    
    var i interface{} = "test"
    s := i.(string)
    fmt.Println("Asserted string:", s)
    
    if val, ok := i.(int); ok {
        fmt.Println("Got int:", val)
    } else {
        fmt.Println("Not an int")
    }
}