go context的四种方法的使用

WithCancel

package main

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

func main() {
	ctx, cancel := context.WithCancel(context.Background())
	//同时取消两个协程
	go doDB1Query(ctx)
	go doDB2Query(ctx)
	time.Sleep(3 * time.Second)
	cancel() //取消两个协程
	for   {
		;
	}
}

func doDB1Query(ctx context.Context) {
	fmt.Println("11")
	for {
		select {
		case <-ctx.Done():
			fmt.Println("11ctx done.")
			return
		default:
			time.Sleep(time.Second)
			fmt.Println("db11 waiting db")
		}
	}
}

func doDB2Query(ctx context.Context) {
	fmt.Println("22")
	for {
		select {
		case <-ctx.Done():
			fmt.Println("22ctx done.")
			return
		default:
			time.Sleep(time.Second)
			fmt.Println("db22 waiting db")
		}
	}
}

WithTimeout

package main

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

func main() {

	timeout := 2 * time.Second
	ctx, cancel  := context.WithTimeout(context.Background(), timeout)
	go Add(ctx)

	fmt.Println("现在开始等待8秒,time=", time.Now().Unix())
	time.Sleep(8 * time.Second)
	fmt.Println("等待8秒结束,准备调用cancel()函数，发现两个子协程已经结束了，time=", time.Now().Unix())
	cancel()// 手动退出还没运行，程序因为超时儿关闭
}


func Add(ctx context.Context){
	for{
		select {
		case <-ctx.Done():
			fmt.Println("退出")
			return
		default:
			time.Sleep(time.Second)
			fmt.Println("6666")
		}
	}
}

 WithValue

package main

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

type Options struct {
	InterVal time.Duration
}

func main() {
	ctx, cancel := context.WithCancel(context.Background())
	valueTX := context.WithValue(ctx, "Options", &Options{1} )
	go doDB2Q(valueTX)
	time.Sleep(3 * time.Second)
	cancel()
	for   {
		;
	}
}

func doDB2Q(ctx context.Context) {
	fmt.Println("22")
	for {
		select {
		case <-ctx.Done():
			fmt.Println("22ctx done.")
			return
		default:
			op := ctx.Value("Options")
			fmt.Println(op)
		}
	}
}

WithDeadline

和WithTimeout类似

package main

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



func main() {
	//十秒后自动退出
	ctx, cancel := context.WithDeadline(context.Background(), time.Now().Add(10 * time.Second))
	defer cancel()
	go DB(ctx)

	for   {
		;
	}
}

func DB(ctx context.Context) {
	fmt.Println("db start")
	for {
		select {
		case <-ctx.Done():
			fmt.Println("db done.")
			return
		default:
			fmt.Println("db ing")
			time.Sleep(time.Second)
		}
	}
}