golang循环打印 dog cat fox

循环打印: dog cat fox

package main

import (
    "fmt"
    "sync"
)

func main() {
    var num int = 3
    dog := make(chan struct{})
    cat := make(chan struct{})
    fox := make(chan struct{})
    wg := &sync.WaitGroup{}
    wg.Add(3)
    go func(n int) {
        defer wg.Done()
        for i := 0; i < n; i++ {
            <-dog
            fmt.Println("dog")
            cat <- struct{}{}
        }
    }(num)
    go func(n int) {
        defer wg.Done()
        for i := 0; i < n; i++ {
            <-cat
            fmt.Println("cat")
            fox <- struct{}{}
        }
    }(num)
    go func(n int) {
        defer wg.Done()
        for i := 0; i < n; i++ {
            fmt.Println("------", i)
            <-fox
            fmt.Println("fox")
            if i < n-1 {
                dog <- struct{}{}
            }
        }
    }(num)
    dog <- struct{}{}
    wg.Wait()
    fmt.Println("finished!!!")
}