Go routine on a changable timer

timer.go

package main

/*
 Example of creating go routine with time based channel - this time can be
 adjusted by the parent, so it can postpone (or bring forwards) whatever the
 child should do. This could be useful for creating a polling mechanism which
 you occasionally want to run sooner.

 The parent creates the channel and passes it to the go routine to wait for 10
 seconds. This channel is used to communicate how long the child should wait
 for. The child creates a channel to act as a timer, and selects on it and
 the channel from the parent. This causes the child to wait for the original
 timer to go off, or for a new timer to be sent from the parent.
*/

import (
	"fmt"
	"time"
)

func waiter(t chan time.Duration) {
	n := make(<-chan time.Time)
	for {
		select {
		case <-n:
			fmt.Println("Child: timer triggered")
			close(t)
			return
		case v := <-t:
			n = time.After(v)
			fmt.Printf("Child: new time seen - %s\n", v)
			break
		}
	}
}

func main() {
	two_seconds := 2 * time.Second
	t := make(chan time.Duration)
	go waiter(t)
	t <- (10 * time.Second)

	fmt.Printf("Parent: sleeping for %s\n", two_seconds)
	time.Sleep(two_seconds)
	fmt.Println("Parent: sending new sleep")
	t <- two_seconds

	fmt.Println("Parent: sleep sent, waiting for child")
	_, open := <-t
	fmt.Printf("Parent: child responded: %s\n", open)
}