go语言学习笔记（三）-蒲公英云

go语言学习笔记（三）

并发

1.通过go关键字创建并发任务

package main
func main(){
    go println("hello word")
}
package main
func main(){
    go println("hello word")
    go func (s string){
        println(s)
    }("hello word")
}

2.与defer一样，goroutine也会因延迟执行而立即计算并复制执行参数。

package main
import "time"
var c int
func counter() int {
    c++
    return c
}
func main(){
    a:= 100
    go func(x, y int){
        time.Sleep(time.Second)
        println("go:",x,y)
    }(a, counter())
    a+=100
    println("main:" , a, counter())
    time.Sleep(time.Second*3)
}

结果

main: 200 2
go: 100 1

3.wait 进程退出时不会等待并发任务结束，可用通道channel进行阻塞，最后发出退出信号

package main
import (
    "time"
)
func main() {
    exit := make(chan struct{})
    go func() {
        time.Sleep(time.Second)
        println("goroutine done.")
        close(exit)
    }()
    println("main...")
    <-exit
    println("main exit")
}

4.sync.WaitGroup的使用

package main
import (
    "sync"
    "time"
)
func main() {
    var wg sync.WaitGroup
    for i:=0;i<10;i++{
        wg.Add(1)
        go func(id int) {
            defer wg.Done()
            time.Sleep(time.Second)
            println("goroutine", id, "done.")
        }(i)
    }
    println("main...")
    wg.Wait()
    println("main exit")
}