App.js

/* ... */
import { Location, Permissions } from 'expo'

const deltas = {
  latitudeDelta: 0.0922,
  longitudeDelta: 0.0421
};

export default App extends Component {
  state = {
    region: null,
    coffeeShops: []
  };

  componentWillMount() {
    this.getLocationAsync();
  }

  getLocationAsync = async () => {
    let { status } = await Permissions.askAsync(Permissions.LOCATION);
    if (status !== 'granted') {
      this.setState({
        errorMessage: 'Permission to access location was denied'
      });
    }

    let location = await Location.getCurrentPositionAsync({});
    const region = {
      latitude: location.coords.latitude,
      longitude: location.coords.longitude,
      ...deltas
    };
    await this.setState({ region });
  }

  render() { /* ... */ }
}