code: func (n *NamedStmt) Queryx(arg interface{}) (*Rows, error) {
  	r, err := n.Query(arg)
  	if err != nil {
  		return nil, err
  	}
  	return &Rows{Rows: r, Mapper: n.Stmt.Mapper, unsafe: isUnsafe(n)}, err
  }
docs: // Queryx using this NamedStmt
  // Any named placeholder parameters are replaced with fields from arg.