Go: Contexts

context.go

package main

import (
	"context"
	"fmt"
	"sync"
	"time"
)

func withCancel() {
	var wg sync.WaitGroup
	ctx, cancel := context.WithCancel(context.Background())
	go func() {
		ch := ctx.Done()
		defer wg.Done()
		fmt.Println("Done: ", <-ch)
	}()
	go func() {
		defer wg.Done()
		d, _ := time.ParseDuration("100ms")
		fmt.Printf("Will manually cancel in %s\n", d)
		time.Sleep(d)
		cancel()
	}()
	wg.Add(2)
	wg.Wait()
}

func withTimeout() {
	var wg sync.WaitGroup
	d, _ := time.ParseDuration("100ms")
	fmt.Printf("Will auto-cancel in %s\n", d)
	ctx, _ := context.WithTimeout(context.Background(), d)
	go func() {
		ch := ctx.Done()
		defer wg.Done()
		fmt.Println("Done: ", <-ch)
	}()
	wg.Add(1)
	wg.Wait()
}

func main() {
	withCancel()
	withTimeout()
}