React Native Expo project

Hello, I would like to track the GPS location of the people using my app but its not working when the app is at the background. I use Expo based on React Native. The tracking should work even if the application is at the background. Expo, since March 2019, offers this feature but I didn't find the way to use it. My app is pretty simple. Its looks like this : import React from 'react'; import { StyleSheet, Text, View } from 'react-native'; import {WebView} from 'react-native'; export default class App extends [login to view URL] { render() { return ( <WebView source={{uri: 'URL of my website'}} geolocationEnabled={true} mediaPlaybackRequiresUserAction={false} style={{marginTop: 20}} /> ); } } const styles = [login to view URL]({ container: { flex: 1, backgroundColor: '#fff', alignItems: 'center', justifyContent: 'center', }, }); The Location Tracking is for the moment assured by my website (via javascript). Regards