package main

import (
    "fmt"
    "os"
    "strings"
)

func main() {
    who := "World!"
    if len(os.Args) > 1 { /* os.Args[0] is "hello" or "hello.exe" */
        who = strings.Join(os.Args[1:], " ")
    }
    fmt.Println("Hello", who)
}