package main
 
import "fmt"
 
func printType(v interface{}) {
    switch val := v.(type) {
    case int:
        fmt.Printf("Integer: %d\n", val*2)
    case string:
        fmt.Printf("String: %s (length: %d)\n", val, len(val))
    case bool:
        fmt.Printf("Boolean: %t\n", val)
    case []int:
        fmt.Printf("Int slice with %d elements\n", len(val))
    default:
        fmt.Printf("Unknown type\n")
    }
}
 
func main() {
    // Type assertion
    var i interface{} = "hello"
    s, ok := i.(string)
    fmt.Printf("Assertion success: %v, value: %s\n", ok, s)
 
    // Failed assertion
    var j interface{} = 42
    str, ok := j.(string)
    fmt.Printf("String assertion success: %v, value: %s\n", ok, str)
 
    printType(100)
    printType("Go rocks")
    printType(true)
    printType([]int{1, 2, 3})
}