Select:

用途: 监听IO操作，当IO操作发生时，触发相应的动作, 与goroutine联合使用

e.g.

package main
import(
    "fmt"
    "time"
)

func main() {
    c := make(chan int)

    go func() {
        time.Sleep(5 * time.Second)
        c <- 10
    }()

    for {
        select {
            case <-c:
            fmt.Print("trigger from chan C")
            return
        }
    }
}