Golang可以安全地切换cmd.Stdout

cmd := exec.Command(path)
    cmd.Dir = dir
    t := time.Now()
    t1 := t.Format("20060102-150405")

    fs,err := os.Create(dir + "/var/log/" + t1 + ".std")
    if err == nil {
        cmd.Stdout = fs
    }

我希望每天轮换日志并更改日志文件
http://golang.org/pkg/os/exec/

// Stdout and Stderr specify the process's standard output and error.
    //
    // If either is nil,Run connects the corresponding file descriptor
    // to the null device (os.DevNull).
    //
    // If Stdout and Stderr are the same writer,at most one
    // goroutIne at a time will call Write.
    Stdout io.Writer
    Stderr io.Writer

从arbitary goroutIne每天更改cmd.Stdout变量是否安全,或者我必须实现将从Stdout复制到另一个文件并切换文件的goroutIne？