Go 学习杂记

select + time.After 超时控制

• https://segmentfault.com/a/1190000015084958

package main

import (
    "time"
    "fmt"
)

func main() {
    ch := make(chan string)

    go func() {
        time.Sleep(time.Second * 2)
        ch <- "result"
    }()

    select {
    case res := <-ch:
        fmt.Println(res)
    case <-time.After(time.Second * 1):
        fmt.Println("timeout")
    }
}

• 使用 channel 来接收 goroutine 返回值

• select 语句阻塞等待最先返回数据的 channel，当先接收到 time.After 的通道数据时，select 则会停止阻塞并执行该 case 的代码。此时就实现了对业务代码的超时处理

等待 channel 完成方法

1、select {}

package main

import (
	"fmt"
	"time"
)

func main() {

	go func() {
		fmt.Println("start channel: sleep 3s")
		time.Sleep(3 * time.Second)
		fmt.Println("end channel: sleep 3s")
	}()

	select {}

}

output

☁  test  go run main.go
start channel: sleep 3s
end channel: sleep 3s
fatal error: all goroutines are asleep - deadlock!

goroutine 1 [select (no cases)]:
main.main()
	/Users/xiechengqi/test/main.go:16 +0x28
exit status 2

2、sync.WaitGroup

package main

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

func main() {

	var wg sync.WaitGroup

	wg.Add(1)
	go func() {
		defer wg.Done()
		fmt.Println("start channel: sleep 3s")
		time.Sleep(3 * time.Second)
		fmt.Println("end channel: sleep 3s")
	}()

	wg.Wait()

}

output

☁  test  go run main.go
start channel: sleep 3s
end channel: sleep 3s

3、chan os.Signal

package main

import (
	"fmt"
	"os"
	"os/signal"
	"syscall"
	"time"
)

func main() {

	go func() {
		fmt.Println("start channel: sleep 3s")
		time.Sleep(3 * time.Second)
		fmt.Println("end channel: sleep 3s")
	}()

	signalChan := make(chan os.Signal, 1)
	signal.Notify(signalChan, syscall.SIGINT, syscall.SIGTERM)
	<-signalChan

}