how to call dart package method from Flutter app - class

Question

I am trying to create a dart package and use it in my few flutter projects. The package is not public it’s a private package. I am trying to understand how to create a package with working on an example. The documentation wasn’t so difficult, but it confuses me, because I am new to this type project.
So, I create private dart package project. My package name is socket_conn. The socket_conn.dart has single export line as export 'src/socket_conn_base.dart'; My socket_conn_base.dart has 1 class and 1 Future method.
My intention is to import this package to my flutter app, send data to EncrptedSocketCommunication and wait EncrptedSocketCommunication returns data from getQuery. It didn’t work.
I am not sure if I am doing right but calling EncrptedSocketCommunication how do I fire getQuery method, so it goes another class under my src folder (getQueryA100) and gets the data. The getQueryA100 has a working and tested code. But when I import this package to my flutter app
İt doesn’t call Future>> getQuery.
My question is how to call dart package method from Flutter app?
import 'csbins_socket/getQueryA100.dart';
List<List<dynamic>> _returnData;
class EncrptedSocketCommunication {
String connectionText;
String queryText;
String parameterText;
EncrptedSocketCommunication(
this.connectionText,
this.queryText,
this.parameterText
);
Future<List<List<dynamic>>> getQuery(String connectionText, String queryText, String parameterText) async {
switch (queryText){
case "QA100": {
_returnData = await getQueryA100(queryText, parameterText);
return _returnData;
}
break;
}
}
}