package main

import (
    "fmt"
    "runtime"
)

func main() {
    fmt.Print("Go runs on ")
    // this is a switch statement.
    // unlike other languages, Go does not
    // automatically "fall through" to other
    // 'case' or 'default' statements unless
    // this is explicitly made to happen

    switch os := runtime.GOOS; os {
        case "darwin":
            fmt.Println("macOS.")
        case "linux":
            fmt.Println("Linux.")
        default:
            fmt.Printf("%s.", os)
    }
}