Flutter: unable to get local issuer certificate HandshakeException: Handshake error in client 

Solution 1

class MyHttpOverrides extends HttpOverrides{
  @override
  HttpClient createHttpClient(SecurityContext context){
    return super.createHttpClient(context)
      ..badCertificateCallback = (X509Certificate cert, String host, int port)=> true;
  }
}

void main(){
  HttpOverrides.global = new MyHttpOverrides();
 class MyHttpOverrides extends HttpOverrides {
@override
HttpClient createHttpClient(SecurityContext context) {
return super.createHttpClient(context)
  ..badCertificateCallback =
      (X509Certificate cert, String host, int port) => true; }}

void main() async {
WidgetsFlutterBinding.ensureInitialized();
HttpOverrides.global = new MyHttpOverrides();
runApp(Myapp());}

Calling MyHttpOverrides() may help you. But should it should be only used in development mode.

This should be used while in development mode, do NOT do this when you want to release to production, the aim of this answer is to make the development a bit easier for you, for production, you need to fix your certificate issue and use it properly, look at the other answers for this as it might be helpful for your case

Solution 2 (for Dio user)

Dio dio = new Dio();
(dio.httpClientAdapter as DefaultHttpClientAdapter).onHttpClientCreate =
    (HttpClient client) {
  client.badCertificateCallback =
      (X509Certificate cert, String host, int port) => true;
  return client;
};

Solution 3

It could be your device time and clock problem. Update your device or change a device.