Go语言并发之WaitGroup的用法详解

type WaitGroup struct {
	// contains filtered or unexported fields
}
// 添加等待信号
func (wg*WaitGroup) Add (delta int)
// 释放等待信号
func (wg*WaitGroup) Done()
// 等待
func (wg*WaitGroup) Wait()

package main
import (
	"net/http"
	"sync"
)
var wg sync.WaitGroup
var urls = []string{
	"https://news.sina.com.cn/",
	"https://www.bilibili.com/",
	"https://www.qq.com/",
}
func main() {
	for _, url := range urls {
		//每一个url启动一个goroutine，同时给wg加1
		wg.Add(1)
		// 启动一个goroutine获取URL
		go func(url string) {
			// 当前goroutine结束后给wg计数减1 ,wg.Done()等价于wg.Add(-1)
			// defer wg.Add(-1)
			defer wg.Done()
			// 发送http get请求并打印http返回码
			resp, err := http.Get(url)
			if err == nil {
				println(resp.Status)
			}
		}(url)
	}
	// 等待所有HTTP获取完成
	wg.Wait()
}

package main
import (
	"fmt"
	"sync"
)
var wg sync.WaitGroup
func main() {
	// 启动一个goroutine就登记+1,启动十个就+10
	wg.Add(10)
	var count = 0
	for i := 0; i < 10; i++ {
		go func() {
			// goroutine结束就登记-1
			defer wg.Done()
			for j := 0; j < 100000; j++ {
				count++
			}
		}()
	}
	// 等待所有登记的goroutine都结束
	wg.Wait()
	// 346730
	fmt.Print(count)
}

package main
import (
	"fmt"
	"sync"
)
var wg sync.WaitGroup
func main() {
	// 定义锁
	var mu sync.Mutex
	wg.Add(10)
	var count = 0
	for i := 0; i < 10; i++ {
		go func() {
			defer wg.Done()
			for j := 0; j < 100000; j++ {
				// 加锁
				mu.Lock()
				count++
				// 解锁
				mu.Unlock()
			}
		}()
	}
	wg.Wait()
	// 1000000
	fmt.Print(count)
}

package main
import (
	"fmt"
	"sync"
)
var wg sync.WaitGroup
type Counter struct {
	sync.Mutex
	Count uint64
}
func main() {
	var counter Counter
	wg.Add(10)
	for i := 0; i < 10; i++ {
		go func() {
			defer wg.Done()
			for j := 0; j < 100000; j++ {
				counter.Lock()
				counter.Count++
				counter.Unlock()
			}
		}()
	}
	wg.Wait()
	// 1000000
	fmt.Print(counter.Count)
}

package main
import (
	"fmt"
	"sync"
)
var wg sync.WaitGroup
type Counter struct {
	mu    sync.Mutex
	count uint64
}
func (c *Counter) Incr() {
	c.mu.Lock()
	c.count++
	c.mu.Unlock()
}
func (c *Counter) Count() uint64 {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.count
}
func main() {
	var counter Counter
	// 启动一个goroutine就登记+1,启动十个就+10
	wg.Add(10)
	for i := 0; i < 10; i++ {
		go func() {
			// goroutine结束就登记-1
			defer wg.Done()
			for j := 0; j < 100000; j++ {
				counter.Incr()
			}
		}()
	}
	// 等待所有登记的goroutine都结束
	wg.Wait()
	// 1000000
	fmt.Print(counter.Count())
}