postal function
It takes a base64 encoded JSON string, decodes it, converts it to a map, gets the keys of the map, converts the keys to a list, and returns a random key from the list
Returns: A random postal code from the list of postal codes.
Implementation
String postal() {
final decodedAddress = base64Decode(postals);
final postalsMap = jsonDecode(
String.fromCharCodes(decodedAddress),
) as Map<String, dynamic>;
final pstals = postalsMap.keys.toList();
return pstals[Random().nextInt(pstals.length)];
}