From 3477d7143d73fc554e55ec43a268794640d6b412 Mon Sep 17 00:00:00 2001
From: Your Name <you@example.com>
Date: Thu, 4 Jul 2024 00:14:36 +0800
Subject: [PATCH] waitGroup

---
 Concurrency/Concurrency  | 17 ++++++++++++++++-
 Concurrency/waitgroup.go | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 Concurrency/waitgroup.go

diff --git a/Concurrency/Concurrency b/Concurrency/Concurrency
index d12fea2..b688231 100644
--- a/Concurrency/Concurrency
+++ b/Concurrency/Concurrency
@@ -10,4 +10,19 @@ golang提供channel用来在多个goroutine之间进行通信。
 
 
 
-只需要在调用函数前加上 go 关键字 即可开启一个goroutine
\ No newline at end of file
+只需要在调用函数前加上 go 关键字 即可开启一个goroutine
+
+
+goroutine对应的函数执行结束了，goroutine就结束了
+main函数执行完毕，由main函数创建的那些goroutine就结束了
+
+如何等待所有的goroutine结束之后再执行主函数？
+sync.waitGroup对象中有三个方法
+var wg sync.waitGroup
+wg.add(1) //计数器加1
+wg.done()//计数器减1
+wg.wait()//等待所有的goroutine结束
+
+
+goroutine与线程
+os线程有固定的栈内存
\ No newline at end of file
diff --git a/Concurrency/waitgroup.go b/Concurrency/waitgroup.go
new file mode 100644
index 0000000..3d5afb1
--- /dev/null
+++ b/Concurrency/waitgroup.go
@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"sync"
+	"time"
+)
+
+//waitGroup
+
+func f() {
+	//生成随机数
+	rand.New(rand.NewSource(time.Now().UnixNano()))
+	for i := 0; i < 5; i++ {
+		r1 := rand.Int()
+		r2 := rand.Intn(10)
+		fmt.Println(r1, r2)
+	}
+
+}
+
+func f1(i int) {
+	defer wg.Done() //任务结束后计数器-1
+	time.Sleep(time.Second * time.Duration(rand.Intn(3)))
+	fmt.Println(i)
+
+}
+
+var wg sync.WaitGroup
+
+func main() {
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go f1(i)
+	}
+	//如何知道这10个goroutine都结束了
+	wg.Wait() //等待wg的计数器减为0
+
+}