disconnect method
Free TonClient and resources should be always run when you don't need client any more
Implementation
void disconnect() {
if (_utils == null) {
throw ('Client core not connected! Use TonClient.connect to open connection!');
}
_tonCore.disconnect();
_utils = null;
_abi = null;
_boc = null;
_crypto = null;
_processing = null;
_tvm = null;
_net = null;
_client = null;
}