gopl.io/ch8/countdown3/countdown.go

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 246.
// Countdown implements the countdown for a rocket launch.
package main
// NOTE: the ticker goroutine never terminates if the launch is aborted.
// This is a "goroutine leak".
import (
"fmt"
"os"
"time"
)
//!+
func main() {
// ...create abort channel...
//!-
abort := make(chan struct{})
go func() {
os.Stdin.Read(make([]byte, 1)) // read a single byte
abort <- struct{}{}
}()
//!+
fmt.Println("Commencing countdown. Press return to abort.")
tick := time.Tick(1 * time.Second)
for countdown := 10; countdown > 0; countdown-- {
fmt.Println(countdown)
select {
case <-tick:
// Do nothing.
case <-abort:
fmt.Println("Launch aborted!")
return
}
}
launch()
}
//!-
func launch() {
fmt.Println("Lift off!")
}