package main

import (
 "fmt"
 "strconv"
 "time"
)

type value struct {
 id int
 op int
 ret chan int
}
var dic map[int]int
var ch chan *value

func readAndWrite2Map() {
 for {
 select{
 case flag := <- ch:

  if flag.op > 0 {
  log.Printf("id: %v, op: %v, ret: %v", flag.id, flag.op, flag.op)
  dic[1] = flag.op
  flag.ret <- dic[1]
  } else if flag.op == 0 {
  log.Printf("id: %v, op: %v, ret: %v", flag.id, flag.op, dic[1])
  flag.ret <- dic[1]
  } else {
  return
  }
 }
 }
}


func out(flag, i, val int) {
 if flag == 0 {
 fmt.Println(strconv.Itoa(i) + "th goroutine read the value is ", val)
 } else {
 fmt.Println(strconv.Itoa(i)+"th goroutine write to the map ", val)
 }
}

func main() {
 dic = make(map[int]int)
 ch = make(chan *value)
 dic[1] = -1
 go readAndWrite2Map()
 for i := 0; i <= 5; i++ {
 if (i % 2) == 0 {
  go func(i int) {
   var tmp value
   for {
   tmp.op = 0
   ch <- &tmp
   out(0, i, <-tmp.ret)
   time.Sleep(time.Millisecond)
   }
  }(i)

 } else {
  go func(i int) {
   var tmp value
   for {
   tmp.op = i
   ch <- &tmp
   out(1, i, <-tmp.ret)
   time.Sleep(time.Millisecond)

   }
  }(i)
 }
 }
 time.Sleep(time.Second * 60)
}