React native JSON Parse error: Unrecognised token '<' GET

When doing a GET request in react native, on a local API I have written I get the error, 'JSON Parse error: Unrecognised token '<''. When doing a GET request via Postman, the JSON I see is:

{"question":"Which three Spaniards played in the 2007 Champions League Final?","answer":"Pepe Reina, Alvaro Arbeloa, Xabi Alonso","id":1}

This is my react native code:

_onPressButtonGET: function() {
    fetch("http://localhost:8088/id/1", {method: "GET"})
    .then((response) => response.json())
    .then((responseData) => {
        AlertIOS.alert(
            "GET Response",
            "Search Query -> " + responseData.question
        )
    })
    .done();
},

render: function() {
    return (
        <View style={styles.container}>
            <TouchableHighlight onPress={this._onPressButtonGET} style={styles.button}>
                <Text>GET</Text>
            </TouchableHighlight>
            <TouchableHighlight onPress={this._onPressButtonPOST} style={styles.button}>
                <Text>POST</Text>
            </TouchableHighlight>
        </View>
    );
},

This is my API's code:

var express = require('express');
var app = express();
var fs = require('fs');
var random = require('random-number-generator')

app.get('/teasers', function (req, res) {
    fs.readFile(__dirname + '/' + 'teasers.json', 'utf8', function (err, data) {
        console.log(data);
        res.end(data);
    });
});

app.get('/teasers/:id', function (req, res) {
    fs.readFile(__dirname + '/' + 'teasers.json', 'utf8', function (err, data) {
        users = JSON.parse(data);
        var user = users['question' + req.params.id];
        console.log(user);
        res.end(JSON.stringify(user));
    });
});

var server = app.listen(8088, function() {
    var host = server.address().address;
    var port = server.address().port;

    console.log("Example app listening at http://localhost:%s", host, port);
});

via jord