code: func (c *Client) Auth(user, pass string) (*gomemcached.MCResponse, error) {
  	res, err := c.AuthList()
  
  	if err != nil {
  		return res, err
  	}
  
  	authMech := string(res.Body)
  	if strings.Index(authMech, "PLAIN") != -1 {
  		return c.Send(&gomemcached.MCRequest{
  			Opcode: gomemcached.SASL_AUTH,
  			Key:    []byte("PLAIN"),
  			Body:   []byte(fmt.Sprintf("\x00%s\x00%s", user, pass))})
  	}
  	return res, fmt.Errorf("auth mechanism PLAIN not supported")
  }
docs: // Auth performs SASL PLAIN authentication against the server.