為什么 Go 在寫入關閉的通道時會出現(xiàn)恐慌？雖然可以使用value, ok := <-channel習語從通道讀取，因此可以測試 ok 結果是否命中封閉通道：// reading from closed channelpackage mainimport "fmt"func main() {    ch := make(chan int, 1)    ch <- 2    close(ch)    read(ch)    read(ch)    read(ch)}func read(ch <-chan int) {    i,ok := <- ch       if !ok {        fmt.Printf("channel is closed\n")        return    }    fmt.Printf("read %d from channel\n", i)}輸出：read 2 from channelchannel is closedchannel is closed在Playground上運行“從封閉頻道讀取”寫入可能關閉的通道更加復雜，因為如果您只是在通道關閉時嘗試寫入，Go 會恐慌：//writing to closed channelpackage mainimport (    "fmt")func main() {    output := make(chan int, 1) // create channel    write(output, 2)    close(output) // close channel    write(output, 3)    write(output, 4)}// how to write on possibly closed channelfunc write(out chan int, i int) (err error) {    defer func() {        // recover from panic caused by writing to a closed channel        if r := recover(); r != nil {            err = fmt.Errorf("%v", r)            fmt.Printf("write: error writing %d on channel: %v\n", i, err)            return        }        fmt.Printf("write: wrote %d on channel\n", i)    }()    out <- i // write on possibly closed channel    return err}輸出：write: wrote 2 on channelwrite: error writing 3 on channel: send on closed channelwrite: error writing 4 on channel: send on closed channel在Playground上運行“寫入封閉頻道”據(jù)我所知，沒有一個更簡單的習慣用法可以在不驚慌的情況下寫入可能已關閉的通道。為什么不？這種讀寫之間的不對稱行為背后的原因是什么？