golang 常见变成问题01

func CopyFile (dst, src string) (w int64, err error) {
srcFile, err := os.Open (src)
defer srcFile.Close ()
if err != nil {
return
}
//using srcFile to do sth
return
}

values := []string{"a", "b", "c"}
for _, v := range values {
go func() {
fmt.Println(v)
}()
}

package main

import (
    "fmt"
    "runtime"
    "time"
)

func main() {

    runtime.GOMAXPROCS(runtime.NumCPU())
    ch := make(chan int,1024)

    go func(ch chan int) {
        for{
            val := <-ch
            fmt.Println("val:",val)
        }
    }(ch)

    tick :=time.NewTicker(1 * time.Second)
    for i := 0;i <30;i++{
        select {
        case ch <-i:
        case <-tick.C:
            fmt.Println("1 Second")
        }
        time.Sleep(200 * time.Millisecond)
    }
    close(ch)
    tick.Stop()
}

//val: 0
//val: 1
//val: 2
//val: 3
//val: 4
//val: 5
//val: 6
//1 Second
//val: 8
//val: 9
//1 Second
//val: 11
//val: 12
//val: 13
//val: 14
//1 Second
//val: 16
//val: 17
//val: 18
//val: 19
//val: 20
//val: 21
//val: 22
//val: 23
//val: 24
//1 Second
//val: 26
//val: 27
//val: 28
//val: 29

func putSignal(ch chan struct{}, sign struct{}) (ok bool) {

select {
case ch <- sign:
ok = true
default:// 省略了会 block
}
}
return