我希望能够取消一个os.stdin读使用上下文，这是不可能的。通常，关闭文件句柄来完成取消操作，但我不想关闭os.stdin
可能的解决办法是：

• 是否可以确定标准输入读取是否会阻塞？
• 线程可以像pthreads那样终止吗？
• 是否应将os.stdin转发到另一个可以关闭的文件句柄？

这是我得到的，丑陋的是scannerThread在上下文取消时仍然运行：

// Keystrokes emits keystroke events
// on g0.Context() shutdown, scannerThread is left running until the next newline
// the lines channel is never closed
func Keystrokes(lines chan<- string, g0 parl.Go) {
  var err error
  defer g0.Done(err)
  defer parl.Recover(parl.Annotation(), &err, parl.NoOnError)

  // stdio.Scan cannot be terminated, so let that thread terminate whenever
  var scanLines parl.NBChan[string]
  go scannerThread(scanLines.Send, g0.Context())

  // consume scannerThread output
  scannerCh := scanLines.Ch()
  done := g0.Context().Done()
  for {
    select {
    case line := <-scannerCh:
      lines <- line
    case <-done:
      return // canceled by context exit
    }
  }
}

// scannerThread reads from os.Stdin and therefore cannot be cancelled.
// send is a non-blocking send function.
// ctx indicates shutdown effective on next os.Stdin newline.
func scannerThread(send func(string), ctx context.Context) {
  var err error
  defer parl.Recover(parl.Annotation(), &err, parl.Infallible)

  scanner := bufio.NewScanner(os.Stdin)
  for scanner.Scan() { // scanner is typically stuck here
    if ctx.Err() != nil {
      return // terminated via context
    }
    send(scanner.Text())
  }

  // scanner had error
  err = scanner.Err()
}