Golang 关闭的Channel读写问题

1.向一个已关闭的channel发送元素会引起panic

panic: send on closed channel

package main

import (
	"sync"
	"time"
)

func main() {
	ch := make(chan struct{})
	close(ch)

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		ch <- struct{}{}
		time.Sleep(time.Second*2)
		wg.Done()
	}()
	
	wg.Wait()
	
}

 

 

2. 在发送端关闭Channel，接收端还会继续接收到通道中的元素

package main

import (
	"sync"
	"fmt"
)

func main() {
	ch := make(chan int,10)
	for i := 0 ; i < 10 ; i++ {
		ch <- i
	}
	close(ch)

	var wg sync.WaitGroup
	wg.Add(1)

	go func() {
		defer wg.Done()
		for v := range ch {
			fmt.Println(v)
		}
	}()

	wg.Wait()
	fmt.Println("over")
}

 

3. select...case... 尝试从close的channel接受数据会直接获取该channel类型的空值

package main

import (
	"fmt"
)

func main() {
	ch := make(chan struct{})
	close(ch)

	select {
	case v, ok := <-ch:
		fmt.Println("ch")
		fmt.Println(v)
		fmt.Println(ok)
	default:
		fmt.Println("default")
	}
}

该示例会走 <-ch case