timeout := make (chan bool, 1)
  go func() {
    time.Sleep(1e9) // sleep one second
    timeout <- true
  }()
  select {
  case <- timeout:
    fmt.Println("timeout!")
  }

ch2 := make (chan int, 1)
  ch2 <- 1
  select {
  case ch2 <- 2:
  default:
    fmt.Println("channel is full !")
  }

package main

import (
  "fmt"
  "time"
)

func main() {
  var errChan = make(chan int)
  //定时2s
  ticker := time.NewTicker(2 * time.Second)
  defer ticker.Stop()
  go func(a chan int) {
    //5s发一个信号
    time.Sleep(time.Second * 5)
    errChan <- 1
  }(errChan)
  LOOP:
    for {
      select {
        case <-ticker.C: {
          fmt.Println("Task still running")
        }
        case res, ok := <-errChan:
          if ok {
            fmt.Println("chan number:", res)
            break LOOP
          }
      }
    }
  fmt.Println("end!!!")
}
//输出结果：
//Task still running
//Task still running
//chan number: 1
//end!!!

select {
  case communication clause :
    statement(s)
  case communication clause :
    statement(s)
  default :
    statement(s)
}

package main
import "fmt"
func fibonacci(c, quit chan int) {
  x, y := 0, 1
  for {
    select {
    case c <- x:
      x, y = y, x+y
    case <-quit:
      fmt.Println("quit")
      return
    }
  }
}
func main() {
  c := make(chan int)
  quit := make(chan int)
  // start a goroutine to print current result
  // no buffer in c and quit channel, so this code
  // would block when this goroutine try to print
  go func() {
    for i := 0; i < 10; i++ {
      fmt.Println(<-c)
    }
    quit <- 0
  }()
  fibonacci(c, quit)
}