how to solve flutter CERTIFICATE_VERIFY_FAILED error while performing a POST request?

Just for the sake of clarity specially for the new comers to flutter/dart, here is what you need to do in order to enable this option globally in your project:

1. In your main.dart file, add or import the following class:

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

2. In your main function, add the following line after function definition:

HttpOverrides.global = new MyHttpOverrides();

This comment was very helpful to pass through this matter

Edit & Update Feb 2021: When this question was earlier asked there were not enough docs and developers to answer. The following answers may be more helpful than this one: Ma'moon Al-Akash Answer, Pedro Massango's Answer & Ken's Answer

If you have not found the solution in these 3 answers, you can try the solution below.

Originally Answered Jan 2019: The correct(but a bad) way to do it ,as I found out, is to allow all certificates.

HttpClient client = new HttpClient();
client.badCertificateCallback = ((X509Certificate cert, String host, int port) => true);

String url ='[email protected]';

Map map = { 
     "email" : "email" , 
     "password" : "password"
};

HttpClientRequest request = await client.postUrl(Uri.parse(url));

request.headers.set('content-type', 'application/json');

request.add(utf8.encode(json.encode(map)));

HttpClientResponse response = await request.close();

String reply = await response.transform(utf8.decoder).join();

print(reply);

If you are using Dio library, just do this:

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