[Go语言] 解析Go的Waitgroup和锁的问题

package main
import (
  "fmt"
)
func main() {
  // 并发执行程序
  go running()
}
func running() {
  fmt.Println("Goroutine")
}

package main
import (
  "fmt"
  "time"
)
func main() {
  // 并发执行程序
  go running()
  time.Sleep(3 * time.Second)
}
func running() {
  fmt.Println("Goroutine")
}

   

• Add()：给计数器添加等待 goroutine 的数量。   
  
• Done()：减少 WaitGroup 计数器的值，应在协程的最后执行。   
  
• Wait()：执行阻塞，直到所有的 WaitGroup 数量变成 0
  

package main 
import ( 
  "fmt” 
  "sync” 
  “time"
) 
func process(i int, wg *sync.WaitGroup) { 
  fmt.Println("started Goroutine ", i) 
  time.Sleep(2 * time.Second) 
  fmt.Printf("Goroutine %d ended\n", i) 
  wg.Done() 
} 
func main() { 
  var wg sync.WaitGroup 
  for i := 0; i < 3; i++ { 
    wg.Add(1) 
    go process(i, &wg) 
  } 
  wg.Wait() 
  fmt.Println("All go routines finished executing”) 
}
//main函数也可以写成如下方式
func main() {
  var wg sync.WaitGroup
  wg.Add(3) //设置计数器，数值即为goroutine的个数
  go process(1, &wg)
  go process(2, &wg)
  go process(3, &wg)
  wg.Wait() //主goroutine阻塞等待计数器变为0
  fmt.Println("All goroutines finished executing")
}

　　deer@192 src % go run hello.go //第1次
started Goroutine  3
started Goroutine  1
started Goroutine  2
Goroutine 2 ended
Goroutine 1 ended
Goroutine 3 ended
All goroutines finished executing
　　deer@192 src % go run hello.go //第2次
started Goroutine  3
started Goroutine  1
started Goroutine  2
Goroutine 1 ended
Goroutine 2 ended
Goroutine 3 ended
All goroutines finished executing
　　deer@192 src % go run hello.go //第3次
started Goroutine  3
started Goroutine  2
started Goroutine  1
Goroutine 3 ended
Goroutine 1 ended
Goroutine 2 ended
All goroutines finished executing

　　fatal error: all goroutines are asleep - deadlock!

var lock sync.Mutex //声明一个互斥锁
 lock.Lock() //加锁
//code...
 lock.Unlock() //解锁