// Sometines we'd like our Go programs to intelligently
// handle [Unix signals](http://en.wikipedia.org/wiki/Unix_signal).
// For example, we might want a server to gracefully
// shutdown when it receives a `SIGTERM`, or a command-line
// tool to stop processing input if it receives a `SIGINT`.
// Here's how to handle signals in Go with channels.

package main

import "fmt"
import "os"
import "os/signal"
import "syscall"

func main() {

    // Go signal notification works by sending `os.Signal`
    // values on a channel. We'll create a channel to
    // receive these notifications (we'll also make one to
    // notify us when the program can exit.)
    sigs := make(chan os.Signal, 1)
    done := make(chan bool, 1)

    // `signal.Notify` registers the given channel to
    // receive notifications of the specified signals.
    signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)

    // This goroutine executes a blocking receive for
    // signals. When it gets one it'll print it out
    // and then notify the program that it can finish.
    go func() {
        sig := <-sigs
        fmt.Println()
        fmt.Println(sig)
        done <- true
    }()

    // The program will wait here until it gets the
    // expected signal (as indicated by the goroutine
    // above sending a value on `done`) and then exit.
    fmt.Println("awaiting signal")
    <-done
    fmt.Println("exiting")
}