code: func (d *deadlineTimer) SetReadDeadline(t time.Time) error {
  	d.mu.Lock()
  	d.setDeadline(&d.readCancelCh, &d.readTimer, t)
  	d.mu.Unlock()
  	return nil
  }
docs: // SetReadDeadline implements net.Conn.SetReadDeadline and
  // net.PacketConn.SetReadDeadline.