goroutine cancel

main.go

package main

import (
	"fmt"
	"time"
)

func main() {
	cancel := make(chan struct{})
	go func() {
		time.Sleep(3 * time.Second)
		fmt.Println("Cancel!")
		cancel <- struct{}{}
		// close(cancel) is also OK!
	}()
	wasCanceled := func() bool {
		select {
		case <-cancel:
			return true
		default:
			return false
		}
	}
	i := 1
	for {
		if wasCanceled() {
			break
		}
		fmt.Printf("i = %v\n", i)
		time.Sleep(100 * time.Millisecond)
		i += 1
	}
}