为什么相同的Go Channel无法启动两次？

Question

Can we start the one decalred channel twice in Go lang ?

package main

import (
    "fmt"
)

func emit(c chan string) {

    words := []string {"The", "quick", "brown", "fox"}

    for _, word := range  words {
        c <- word
    }
    close(c)
}

In the function main If i try to use the same channel twice i'm getting default value of that channel

func main() {

    wordChannel := make(chan string)

    go emit(wordChannel)

    for word := range wordChannel {
        fmt.Printf("%s ", word)
    }

    go emit(wordChannel)
    word1 := <-wordChannel
    fmt.Printf("%s" , word1) // prints Default value
}

Output

So to use it again i've to declare another channel. If this is not an error why this was done in the Go Lang. ? i'm using go -lang version 1.6

Answer 1

Channels are not "started", channels simply exist and are in one of two states:

• "open" in which case you can send values to them (and receive the values sent), or
• "closed" in which you cannot send and receiving from a closed channel results in "the-zero-value, false".

A once closed channel stays closed forever. So yes, you have to make a new channel, there is no "reopen" in Go.