private DataSource getDataSource() throws Exception {
        // Taken from Guava Suppliers.memoize()
        if (!dataSourceInitialized) {
            synchronized (this) {
                if (!dataSourceInitialized) {
                    DataSource ds = createDataSource();
                    dataSource = ds;
                    dataSourceInitialized = true;
                    return ds;
                }
            }
        }
        return dataSource;
    }
Convenience method to attach an extension (such as a SqlObject) to the shared handle.
testing/src/main/java/org/jdbi/v3/testing/junit5/JdbiExtension.java