API key for flutter code example

Example 1: flutter ios set google maps

import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State {
  GoogleMapController mapController;

  final LatLng _center = const LatLng(45.521563, -122.677433);

  void _onMapCreated(GoogleMapController controller) {
    mapController = controller;
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Maps Sample App'),
          backgroundColor: Colors.green[700],
        ),
        body: GoogleMap(
          onMapCreated: _onMapCreated,
          initialCameraPosition: CameraPosition(
            target: _center,
            zoom: 11.0,
          ),
        ),
      ),
    );
  }
}

Example 2: google maps for flutter

dependencies:
  google_maps_flutter: ^1.0.2

Example 3: how to use api key in flutter

Try to change http.Response response = await http.get(cryptoUrl); to

http.Response response = await http.get(cryptoUrl, 
headers: {"X-CMC_PRO_API_KEY": "cab79c7b-52e9-4e4b-94fc-b0f32da14799"});

For more info check this link.