golang学习笔记——context库

WithCancel(主进程控制子协程关闭)

package main

import (

"context"

"fmt"

"sync"

"time"

)

var wg sync.WaitGroup

func f(ctx context.Context) {

defer wg.Done()

LOOP:

for {

fmt.Println("hello world")

time.Sleep(time.Millisecond * 500)

select {

case <-ctx.Done():

break LOOP

default:

}

}

}

func main() {

ctx, cancel := context.WithCancel(context.Background())

wg.Add(1)

go f(ctx)

time.Sleep(time.Second * 5)

//通知子协程退出

cancel()

wg.Wait()

}

WithTimeout(超时关闭)

package main

import (

"context"

"fmt"

"sync"

"time"

)

var wg sync.WaitGroup

func f(ctx context.Context) {

defer wg.Done()

LOOP:

for {

fmt.Println("hello world")

time.Sleep(time.Millisecond * 500)

select {

case <-ctx.Done(): //50毫秒自动调用

break LOOP

default:

}

}

}

func main() {

ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)

//通知子协程退出

defer cancel()

wg.Add(1)

go f(ctx)

time.Sleep(time.Second * 5)

wg.Wait()

}

WithValue （key值不能为基础类型，应该用用户自定义的类型）

package main

import (

"context"

"fmt"

"sync"

"time"

)

type cjp string

var wg sync.WaitGroup

func f(ctx context.Context) {

defer wg.Done()

LOOP:

for {

fmt.Println(ctx.Value(cjp("mt")))

fmt.Println("hello world")

time.Sleep(time.Millisecond * 500)

select {

case <-ctx.Done(): //50毫秒自动调用

break LOOP

default:

}

}

}

func main() {

ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)

defer cancel()

ctx = context.WithValue(ctx, cjp("mt"), "cuijiapeng")

wg.Add(1)

go f(ctx)

time.Sleep(time.Second * 5)

wg.Wait()

}