golang面试题：对已经关闭的的chan进行读写，会怎么样？为什么？

package main

func main() {
	ch := make(chan int, 3)
	close(ch)
	ch <- 1
}



panic: send on closed channel                               
                                                            
goroutine 1 [running]:                                      
main.main()                                                 
        D:/goproject/src/github.com/leetcode/test.go:6 +0x452. 读已经关闭的 chan

进程 已完成，退出代码为 2

package main

import "fmt"

func main() {
	fmt.Println("以下是数值chan")
	c1 := make(chan int, 3)
	c1 <- 1
	close(c1)
	num, ok := <-c1
	fmt.Printf("num=%v,ok=%v", num, ok)
	num1, ok1 := <-c1
	fmt.Printf("num1=%v,ok1=%v", num1, ok1)
	num2, ok2 := <-c1
	fmt.Printf("num2=%v,ok2=%v", num2, ok2)

	fmt.Println("以下是字符串的chan")
	c2 := make(chan string, 3)
	c2 <- "abc"
	close(c2)
	str, ok := <-c2
	fmt.Printf("str=%v,ok=%v", str, ok)
	str1, ok1 := <-c2
	fmt.Printf("str1=%v,ok1=%v", str1, ok1)
	str2, ok2 := <-c2
	fmt.Printf("str2=%v,ok2=%v", str2, ok2)

}

num=1,ok=true
num1=0,ok1=false
num2=0,ok2=false

str="abc",ok=true
str1="",ok1=false
str2="",ok2=false

//src/runtime/chan.go/chansend
	if c.closed != 0 {
		unlock(&c.lock)
		panic(plainError("send on closed channel"))
	}