Golang多线程打印ABC

package main

import (
    "fmt"
    "sync"
)

func ThreeG() {
    var ch1, ch2, ch3 = make(chan struct{}), make(chan struct{}), make(chan struct{})
    var wg sync.WaitGroup
    wg.Add(3)

    go func(s string) {
        defer wg.Done()
        for i := 1; i <= 3; i++ {
            <-ch1
            fmt.Println(s)
            ch2 <- struct{}{}
        }
        <-ch1
    }("A")

    go func(s string) {
        defer wg.Done()
        for i := 1; i <= 3; i++ {
            <-ch2
            fmt.Println(s)
            ch3 <- struct{}{}
        }
    }("B")

    go func(s string) {
        defer wg.Done()
        for i := 1; i <= 3; i++ {
            <-ch3
            fmt.Println(s)
            ch1 <- struct{}{}
        }
    }("C")

    // 在向chan写入数据时，会阻塞当前协程，直到其他协程从该chan中读取了数据。
    ch1 <- struct{}{}
    wg.Wait()
}

func NG(n int) {
    chanQueue := make([]chan struct{}, n)
    for i := 0; i < n; i++ {
        chanQueue[i] = make(chan struct{})
    }
    var wg sync.WaitGroup
    wg.Add(n)
    for i := 0; i < n; i++ {
        var preChan chan struct{}
        if i == 0 {
            preChan = chanQueue[n-1]
        } else {
            preChan = chanQueue[i-1]
        }
        curChan := chanQueue[i]
        go func(i byte, preChan, curChan chan struct{}, index int) {
            defer wg.Done()
            for k := 0; k < 5; k++ {
                <-preChan
                fmt.Printf("%c\n", i)
                curChan <- struct{}{}
            }

            if index == 0 {
                <-chanQueue[n-1]
            }

        }('A'+byte(i), preChan, curChan, i)
    }
    chanQueue[n-1] <- struct{}{}

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

func main() {
}