code: func WithVersion(v string) MarshalOption {
  	return func(c *MarshalConfig) error {
  		switch v {
  		case V1, V2:
  			c.Version = v
  			return nil
  		default:
  			return trace.BadParameter("version '%v' is not supported", v)
  		}
  	}
  }
docs: // WithVersion sets marshal version