GO语言练习：channel select 超时机制

1、代码

2、运行

3、解析

---

 

1、代码

package main

import (
    "time"
    "fmt"
)

func waitFor(ch chan int) {
    fmt.Println(time.Now(), "writing ...")
    time.Sleep(1e9)
    ch <- 10
    fmt.Println(time.Now(), "wrote ...")
}

func main() {
    var a chan int = make(chan int)
    var b chan int = make(chan int)
    var ch chan int = make(chan int)

    go waitFor(ch)

    var r int = 0
    fmt.Println(time.Now(), "select ...")
    select {
    case x := <-a :
        fmt.Println(time.Now(), "read from a...")
        r = x
    case x := <-b :
        fmt.Println(time.Now(), "read from b...")
        r = x
    case x := <-ch :
        fmt.Println(time.Now(), "read from ch...")
        r = x
    }
    fmt.Println(time.Now(), "select over.., r = ", r)
    time.Sleep(1e9)
    fmt.Println(time.Now(), "over..")
}

2、运行

$ go run timeout.go 
2015-07-19 00:35:23.859684465 +0800 CST select ...
2015-07-19 00:35:23.861022451 +0800 CST writing ...
2015-07-19 00:35:24.864462549 +0800 CST wrote ...
2015-07-19 00:35:24.865185396 +0800 CST read from ch...
2015-07-19 00:35:24.874655353 +0800 CST select over.., r =  10
2015-07-19 00:35:25.888486739 +0800 CST over..

3、解析

　　1）主线程中的select开始运行，对select中的3个channel进行阻塞等待

　　2）在线程（协程）waitFor中向ch写入数据

　　3）select收到数据，进行读取

　　4）主线程退出