Get x-requestDigest Value by using NTML authentication

How can i get X-REQUESTDIGEST value in NTML authentication response I am new with Node.js

Here is my code to fetch data from SharePoint

        httpntlm.get({
            url: "http://xxx/_api/web/lists/GetByTitle('xxx')/items(1)",
            username: 'xxx',
            password: 'xxx',
            workstation: '',
            domain: 'xxx'
        }, function (err, res){ 

         if(res.headers['X-RequestDigest']==null)
        response.send(JSON.stringify('www-authenticate not found on response of second request'));

    });   

I want to get x-requestdigest value to please help to find it out. Sorry for poor English