Highcharts Export Service Gantt Chart not working - node.js

Question

Attempting to pilot a server-side render of a gantt chart using highcharts-export-server, but unable to get the series data to render at all.
As per the docs, I've tried running the export via commandline and as a node module, but I always get an empty graph with the title, subtitle and series name displaying, but none of the actual data.
Failed Gantt Render
All the basic line graph example configurations work and I'm able to render the chart using the Highcharts.ganttChart method via the browser, so I believe it's specific to the Gantt chart configuration for the export server, or related to the millisecond date conversion (as you can see in the screenshot, the X Axis is not rendering as dates, but rather plain numbers). As per suggestions on other threads, I ran build.js in the node_modules/highcharts-export-server, globally for the commandline attempt and project-locally for the node module attempt, making sure to enable the both the gantt and moment libraries, but that didn't help either.
Including my options json below. I haven't been able to find a gantt config example specifically for the export server, so this is my best attempt to interpolate what they'd be:
{
"title": {
"text": "Gantt PoC"
},
"subtitle": {
"text": "Timeline"
},
"series": [
{
"name": "Gantt Demo",
"type": "gantt",
"data": [
{
"name": "Demo Task 1",
"id": "demo_task_1",
"start": 1564113600000,
"end": 1564718400000
},
{
"name": "Demo Task 2",
"id": "demo_task_2",
"start": 1564113600000,
"end": 1564718400000
}
]
}
],
"xAxis": {
"min": 1563681600000,
"max": 1571803200000
}
}
Please let me know if there's anything obviously wrong with my config, if I missed any crucial steps to prep the environment, or any ideas you may have for me to troubleshoot. Thanks!

Answer 1

i also tried to generate image using ganttchart, just i tried constructor which you suggested working perfectly, Thanks.
highcharts-export-server --infile gantt.json --outfile gantt.png --type png --constr ganttChart
actually i tried with HTTP Server as well, working perfectly. Thanks #pawel_d
const fs = require("fs");
const chartExporter = require('highcharts-export-server');
chartExporter.initPool();
const chartDetails = {
type: "png",
constr : 'ganttChart',
options: {
series: [{
data: [{
start: 1,
end: 10
}]
}]
}
};
chartExporter.export(chartDetails, (err, res) => {
// Get the image data (base64)
let imageb64 = res.data;
// Filename of the output
let outputFile = "bar.png";
// Save the image to file
fs.writeFileSync(outputFile, imageb64, "base64", function(err) {
if (err) console.log(err);
});
console.log("Saved image!");
chartExporter.killPool();
});