SQLite JDBC getGeneratedKeys() race condition

test.groovy

Class.forName('org.sqlite.JDBC')

import groovy.sql.Sql
import java.sql.*

def sql = Sql.newInstance('jdbc:sqlite::memory:', [:] as Properties, 'org.sqlite.JDBC')
sql.execute('drop table if exists test')
sql.execute('create table test (key integer primary key, value string)')

def connection = sql.connection
connection.autoCommit = false

def query = "insert into test (value) values ('foo')"

def lock = new Object()
def t = { ->
    def count = 1000
    while (count-- > 0) {
    //synchronized(lock) {
        def statement = connection.prepareStatement(query);
        statement.executeUpdate();
        def resultSet = statement.getGeneratedKeys();
        connection.commit();
        
        if (resultSet.next()) {
            //println "${Thread.currentThread()} ${resultSet.getLong(1)}";
        } else {
            println "${Thread.currentThread()} no result"
        }
        resultSet.close();
        statement.close();
    //}
    }
}

def t1 = Thread.start(t)
def t2 = Thread.start(t)
t1.join()
t2.join()

connection.close();