Google Gantt Chart

I am using the Gantt Chart provided by Google.

I have added a listener to when I click on any of the elements or entity in attempt to return the row/columns data, but it is returning empty,

    function selectHandler() {
        var selectedItem = chart.getSelection();
        if (selectedItem) {
            console.log(selectedItem);
        }
    }

    google.visualization.events.addListener(chart, 'select', selectHandler);

Here is my attempt on jsfiddle: https://jsfiddle.net/30cuaarb/