node.js https module "unable to determine the domain name"

I am getting

unable to determine the domain name

error when using https.get in node.js application.

My code is below:

const options = {
                    hostname: hostname,
                    port: 443,
                    path: remotePDFFilePath,
                    method: 'GET'
                };
https.get(hostname + remotePDFFilePath, res => {
    res.setEncoding("base64");
    let body = "";
    res.on("data", data => {
        body += data;
    });
    res.on("end", () => {
        callback(null, {
            status: 1,
            response: body.toString('base64')
        });
    });
});

I have tried searching Google and StackOverflow but did not find any relevant information. I tried changing https module with http but got he same error.

The value for hostname is "subdomain.domain.org" and the value for remotePDFFilePath is "/January Folder/Last, First DocID.pdf".