更改指向* os.File的指针

Question

I have rotated files, and I need change files periodically, but I can't renew my pointer to file

var (
  file          *os.File
)

func init() {
    file, err = os.Create(fileName)
}

func main() {
  ticker = time.NewTicker(time.Second * 6)
  defer ticker.Stop()

  go func(file *os.File) {
      <- ticker.C
      fn := fmt.Sprintf("%d%s", time.Now().Unix(), ".txt")
      file, _ = os.Create(fn)
  }(file)

  http.HandleFunc("/go", goHandler)
}

func goHandler(w http.ResponseWriter, r *http.Request) {
  fmt.Printf("hand File: %v
", *file)
  // when handler triggered file stay the same
  file.WriteString(myPayload)
}

it changes inside goroutines, but it doesn't react in handler, so the file stays the same all time.

Suggest, pls, how I can change pointer to *os.File

Answer 1

In your code, the goroutine only runs once. So it creates a single new file and does nothing more - which means *file only changed once.

You should change <- ticker.C to for _ = range ticker.C { ... }.

And also, you should guard changing and reading values from *file with a sync.Mutex, because there is a data race between two goroutine.