code: func (t *terminal) GetWinSize() (*term.Winsize, error) {
  	t.mu.Lock()
  	defer t.mu.Unlock()
  	if t.pty == nil {
  		return nil, trace.NotFound("no pty")
  	}
  	ws, err := term.GetWinsize(t.pty.Fd())
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	return ws, nil
  }
docs: // GetWinSize returns the window size of the terminal.