协程实现顺序打印123

参考解析

题目来源：

答案：

package main
import "fmt"
var one = make(chan struct{}, 1)
var two = make(chan struct{}, 1)
var three = make(chan struct{}, 1)
var done = make(chan struct{})
func PrintOne() {
    defer close(one)
    for i := 0; i < 10; i++ {
        <-three
        fmt.Println("1")
        one <- struct{}{}
    }
}
func PrintTwo() {
    defer close(two)
    for i := 0; i < 10; i++ {
        <-one
        fmt.Println("2")
        two <- struct{}{}
    }
}
func PrintThere() {
    defer close(three)
    for i := 0; i < 10; i++ {
        <-two
        fmt.Println("3")
        three <- struct{}{}
    }
    done <- struct{}{}
}
func main() {
    defer close(done)
    three <- struct{}{}
    go PrintOne()
    go PrintTwo()
    go PrintThere()
    <-done
}