Crashed in bindStmtArgs(), when using the Server package to forward Execute statements from sysbench

[rfyim]

I have implemented a proxy for forwarding queries using the Server package. The ServerHandler is implemented as follows:

type ServerHandler struct {
	Conn  *client.Conn
}

func NewServerHandler(cfg Config) (*ServerHandler, error) {
	conn, err := client.Connect(fmt.Sprintf("%s:%d", cfg.Host, cfg.Port), cfg.User, cfg.Password, "")
	if err != nil {
		return nil, err
	}
	if err = conn.Ping(); err != nil {
		return nil, err
	}
	return &ServerHandler{
		Conn: conn,
	}, nil
}

func (h ServerHandler) UseDB(dbName string) error {
	return h.Conn.UseDB(dbName)
}

func (h ServerHandler) HandleQuery(query string) (*mysql.Result, error) {
	return h.Conn.Execute(query)
}

func (h ServerHandler) HandleFieldList(table string, fieldWildcard string) ([]*mysql.Field, error) {
	return h.Conn.FieldList(table, fieldWildcard)
}
func (h ServerHandler) HandleStmtPrepare(query string) (int, int, interface{}, error) {
	stmt, err := h.Conn.Prepare(query)
	if err != nil {
		return 0, 0, nil, err
	}
	return stmt.ParamNum(), stmt.ColumnNum(), stmt, nil
}
func (h ServerHandler) HandleStmtExecute(context interface{}, query string, args []interface{}) (*mysql.Result, error) {
	return context.(*client.Stmt).Execute(args...)
}

func (h ServerHandler) HandleStmtClose(context interface{}) error {
	return context.(*client.Stmt).Close()
}

func (h ServerHandler) HandleOtherCommand(cmd byte, data []byte) error {
	return mysql.NewError(
		mysql.ER_UNKNOWN_ERROR,
		fmt.Sprintf("command %d is not supported now", cmd),
	)
}

Unfortunately, it crashed in (c *Conn) bindStmtArgs() when I was testing with sysbench. It seems that when repeatedly executing the same statement with the same parameters, the EXECUTE message indicates that there is no need to re-bind the parameters, but the implementation of handleStmtExecute does not save the types and values of the parameters from the previous execution of the statement.