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