package main
import (
 "fmt"
 "time"
 "os"
)
func launch() {
 fmt.Println("nuclear launch detected")
}
func commencingCountDown(canLunch chan int) {
 c := time.Tick(1 * time.Second)
 for countDown := 20; countDown > 0; countDown-- {
  fmt.Println(countDown)
  <- c
 }
 canLunch <- -1
}
func isAbort(abort chan int) {
 os.Stdin.Read(make([]byte, 1))
 abort <- -1
}
func main() {
 fmt.Println("Commencing coutdown")
 abort := make(chan int)
 canLunch := make(chan int)
 go isAbort(abort)
 go commencingCountDown(canLunch)
 select {
 case <- canLunch:
 case <- abort:
  fmt.Println("Launch aborted!")
  return
 }
 launch()
}

timeout := make(chan bool, 1)
go func() {
 time.Sleep(1e9)
 timeout <- true
} ()
 
select {
 case <- ch:
  //从ch中读取数据
 case <-timeout:
  //ch一直没有数据写入，超时触发timeout
}

func main() {
 var a chan string
 a =make(chan string)
 go sendDataTo(a)
 go timing()
 getAchan(10*time.Second,a) 
}
 
func sendDataTo(a chan string) {
 for {
   a <- "我是a通道的数据"
  time.Sleep(1e9 *3)
 }
}
 
//在一定时间内接收不到a的数据则超时
func getAchan(timeout time.Duration, a chan string) {
 var after <-chan time.Time
 loop:
 after = time.After(timeout)
 for{
  fmt.Println("等待a中的数据，10秒后没有数据则超时")
  select {
  case x :=<- a:
   fmt.Println(x)
   goto loop
  case <-after:
   fmt.Println("timeout.")
   return
  }
 }
}
func timing() {
 //定时器，10秒钟执行一次
 ticker := time.NewTicker(10 * time.Second)
 for {
  time := <-ticker.C
  fmt.Println("定时器====>",time.String())
 }
}