Why can't oracle autonomously return the id of inserted data?

Question

I confirmed that the data of the id column of the data inserted with the above sql was returned to the Oracle console window.

declare
  tmp_id number;
begin
  insert into users(nickname, platform, socialKey) values('test', 'test', 'test')
  returning id into tmp_id;
   DBMS_OUTPUT.PUT_LINE(tmp_id);
end;

The id value of the normally inserted data row is returned.

func TestTemp(t *testing.T) {
    envSetting()

    db := database.DatabaseInstance()
    defer db.Close()

    var userCount int
    db.QueryRow(`
    SET SERVEROUTPUT ON
    declare
        tmp_id number;
    begin
        insert into users(nickname, platform, socialKey) values('test', 'test', 'test')
        returning id into tmp_id;
        DBMS_OUTPUT.PUT_LINE(tmp_id);
    end;
    `).Scan(&userCount)

    t.Log(userCount)

}

return data :

Running tool: /opt/homebrew/bin/go test -timeout 30s -run ^TestTemp$ github.com/temp/temp/test/auth

=== RUN   TestTemp
    /Users/temp/project/temp/test/auth/user_test.go:169: 0
--- PASS: TestTemp (0.22s)
PASS
ok      github.com/temp/temp/test/auth  0.366s


> 2023. 1. 16. 오전 12:24:50에 테스트 실행이 종료됨 <

However, when I run the above code in golang, only 0 is returned. Could you please check what part is wrong?