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")
}

 

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