Javascript + Rest + Google Chart: g is undefined

I am coding a website getting data from an home made API and publishing that on a google chart.

on my chart area, I get a text or a red background “g is undefined”.

It is driving me crazy, any clue of what I am doing wrong?

google.charts.setOnLoadCallback(drawChart);
var chart

function drawChart() {

    var data = new google.visualization.DataTable();
    data.addColumn('string', 'Date');
    data.addColumn('number', 'Positive');
    data.addColumn('number', 'Negative');
    data.addColumn('number', 'Mixed');
    data.addColumn('number', 'Neutral');

    var request = new XMLHttpRequest()

    // Open a new connection, using the GET request on the URL endpoint
    request.open("POST", apiEndPoint + "/dailystats", true);
    request.setRequestHeader('Content-Type', 'application/json');
    request.send(JSON.stringify({"media":media,"period":parseInt(period)}));


    request.onload = function() {
    var restcall = JSON.parse(this.response)
        if (request.status >= 200 && request.status < 400) {
            restcall.forEach(metric => {
                data.addRows([[metric.date,metric.sentiments.positive,metric.sentiments.mixed,metric.sentiments.neutral,metric.sentiments.negative]])
            })
        }
    }
    var options = {
    chart: {
        title: 'Box Office Earnings in First Two Weeks of Opening',
        subtitle: 'in millions of dollars (USD)'
    },
    width: 900,
    height: 500
    };

    chart = new google.charts.Line(document.getElementById('linechart_frame'));

    chart.draw(data, google.charts.Line.convertOptions(options));
}```

Thanks!