How to make web service calls in Expressjs?

app.get('/', function(req, res){

var options = {
  host: 'www.google.com'
};

http.get(options, function(http_res) {
    http_res.on('data', function (chunk) {
        res.send('BODY: ' + chunk);
    });
    res.end("");
});

});

I am trying to download google.com homepage, and reprint it, but I get an "Can't use mutable header APIs after sent." error

Anyone know why? or how to make http call?