golang chan 超时

package main

import (
    "fmt"
    "time"
)

var ch chan int = make(chan int, 1)

func main() {
    go aaa()

    select {
    case <-ch: //拿到锁
        fmt.Println("call")
    case <-time.After(5 * time.Second): //超时5s
        fmt.Println("5 sec call")
    }
}

func aaa() {
    time.Sleep(time.Second * 3)
    ch <- 1
}