code: func (c *Conn) Close() error {
  	c.mu.Lock()
  	if c.shutdown || c.closing {
  		c.mu.Unlock()
  		return ErrClosed
  	}
  	c.closing = true
  	c.mu.Unlock()
  	return c.stream.Close()
  }
docs: // Close closes the JSON-RPC connection. The connection may not be
  // used after it has been closed.