package main

import (
	"fmt"
	"sync"
	"time"
)

func main() {
	s := []string{"A", "B", "C"}
	var conds = make(map[string]*sync.Cond, len(s))
	for _, item := range s {
		conds[item] = sync.NewCond(new(sync.Mutex))
	}
	wg := sync.WaitGroup{}
	for i, item := range s {
		wg.Add(1)
		go func(index int, x string) {
			wg.Done()
			c.L.Lock()
			for i := 0; i < 10; i++ {
				c := conds[x]
				c.Wait()
				fmt.Println(i, x)
				conds[s[(index+1)%3]].Signal()
			}
			c.L.Unlock()
		}(i, item)
	}
	wg.Wait()
	conds["A"].Signal()
	time.Sleep(time.Hour)
}