How to get output REFCURSOR in package oracle with golang ("github.com/sijms/go-ora/v2")

i have a package in oracle

    CREATE OR REPLACE PACKAGE PKG_TEST IS
    TYPE REFCURSOR IS REF CURSOR;
    PROCEDURE PROC_GET_DUAL(P_CUR OUT REFCURSOR);
end PKG_TEST;
CREATE OR REPLACE PACKAGE BODY PKG_TEST is
    PROCEDURE PROC_GET_DUAL(
        P_CUR OUT REFCURSOR)
        IS
    BEGIN
        OPEN P_CUR FOR
            select * from dual;
    END PROC_GET_DUAL;
end PKG_TEST;

and i use golang ("github.com/sijms/go-ora/v2") to connect oracle and ping success. I call package such as

var cursor go_ora.RefCursor
fmt.Println(db.Ping())
statement := `begin :x := PKG_TEST.PROC_GET_DUAL(); end;`
_, err := db.Exec(statement, sql.Out{Dest: &cursor})
//check errors

defer cursor.Close()
rows, err := cursor.Query()
// check for error

var (
    var1 string
)
for rows.Next_() {
    err = rows.Scan(&var1)
    // check for error
    fmt.Println(var1)
}

I followed the instructions in https://github.com/sijms/go-ora/blob/master/README.md and got this

Thank you for your help and sorry my English because English is not my native language

You also need to pass the out param to the procedure.

statement := `begin PKG_TEST.PROC_GET_DUAL(:1); end;`
_, err := db.Exec(statement, sql.Out{Dest: &cursor})