post method
void
post()
Implementation
void post(String uri, String contract, void Function(String, int) onSuccess,
void Function(String, int) onError) {
_idCounter++;
_requestResultCbMap[_idCounter] = onSuccess;
_requestErrorCbMap[_idCounter] = onError;
_channel.invokeMethod('post', <String, dynamic>{
"uri": uri,
"contract": contract,
"requestId": _idCounter
});
}