Shelf_router server example with CORS enabled

main.dart

import 'package:shelf_router/shelf_router.dart';
import 'package:shelf/shelf.dart';
import 'package:shelf/shelf_io.dart' as io;

void start() async {
  // Initiate server
  const port = 8081;
  final app = Router();

  // CORS Settings
  const corsHeaders = {
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Methods': 'GET, POST, DELETE, OPTIONS',
    'Access-Control-Allow-Headers': 'Origin, Content-Type',
  };

  app.get('/', (Request request) async {
    return Response.ok(
      'Hello World',
      headers: {
        'Content-Type': 'application/json',
        ...corsHeaders,  // add corsHeaders to response headers of each route
      },
    );
  });

  // Set CORS headers with every request
  final handler = Pipeline().addMiddleware((innerHandler) {
    return (request) async {
      final response = await innerHandler(request);
      print(request.headers);

      // Set CORS when responding to OPTIONS request
      if (request.method == 'OPTIONS') {
        return Response.ok('', headers: corsHeaders);
      }

      // Move onto handler
      return response;
    };
  }).addHandler(app.handler);

  await io.serve(handler, 'localhost', port);

  print('Server listening on port $port');
}