contexts: why Go's context is typically needed

main.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"time"
)

func main() {
	in := make(chan bool)

	go func() {
		reader := bufio.NewReader(os.Stdin)
		fmt.Print("Enter to cancel: ")
		_, _ = reader.ReadString('\n')
		in <- true
		in <- true
	}()

	go sleepAndTalk(in, 5*time.Second, "hello!")
	go sleepAndTalk(in, 5*time.Second, "hello!")

	time.Sleep(6 * time.Second)
}

func sleepAndTalk(c chan bool, t time.Duration, msg string) {
	after := time.After(t)
	select {
	case <-after:
		fmt.Println(msg)
	case <-c:
		fmt.Println("got cancel")
	}
}