example how to cancel, timeout, ctrl + c with cleaning after an operation that lasts

gistfile1.txt

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"os/signal"
	"strconv"
	"time"
)

func main() {
	ctx := context.Background()
	ctx, cancel := context.WithCancel(ctx)

	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)

	defer func() {
		signal.Stop(c)
		cancel()
	}()

	go func() {
		<-c
		fmt.Println("stop")
		cancel()
	}()

	longRunningOperation(ctx)
}

func longRunningOperation(ctx context.Context) {
	f, err := os.Create("test")
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()
	var i int
	var undo bool
work:
	for {
		select {
			// cancelable branch
		case <-ctx.Done():
			fmt.Println("canceled")
			undo = true
			break work
			// timeout branch
		case <-time.After(3 * time.Second):
			fmt.Println("timeout")
			undo = true
			break work
			// working branch
		default:
			fmt.Println("working", i)
			time.Sleep(100 * time.Millisecond)
			_, err := f.WriteString(strconv.Itoa(i) + "\n")
			// on error clear working's result
			if err != nil {
				undo = true
				break work
			}
			// finally work done flawlessly
			if i > 100{
				undo = false
				break work
			}
			i++
		}
	}
	if undo {
		fmt.Println("longRunningOperation result will be cleared")
		f.Truncate(int64(0))
		return
	}

	fmt.Println("longRunningOperation finished")
}