Call A Function Automatically When App Starts Everytime Using Flutter

import 'package:flutter/material.dart';
import 'dart:io' show Platform;
void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.amber,
            title: Text("Call a Function Everytime When App Starts"),
          ),
          body: CustomView()
      ),
    );
  }
}

class CustomView extends StatefulWidget {
  CustomViewWidget createState() => CustomViewWidget();
}
class CustomViewWidget extends State {
  @override
  void initState() {
    showAlert(context);
    super.initState();
  }
  Future showAlert(BuildContext context) async {
    await Future.delayed(Duration(seconds: 6));
    showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: new Text('Welcome To Our App :) .'),
          actions: <Widget>[
            FlatButton(
              child: new Text("OK"),
              onPressed: () {
                Navigator.of(context).pop();
              },
            ),
          ],
        );
      },
    );
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.black,
      body: Center(
          child: Text('Call A Function Automatically When App Starts Everytime',
            style: TextStyle(fontSize: 22,color: Colors.white), textAlign: TextAlign.center,)
      ),
    );
  }

}