How to supply TextField initial value on flutter via async load.

sample.dart

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:flutter_secure_storage/flutter_secure_storage.dart';

class SamplePage extends StatefulWidget {

  @override
  State<StatefulWidget> createState() => _SamplePageWidgetState();
}

class _SamplePageWidgetState extends State<LoginPage> {
  final TextEditingController _email_controller = TextEditingController();

  @override
  void initState() {
    super.initState();

  }
  void setLoginInfo() async {
    FlutterSecureStorage st = new FlutterSecureStorage();
    String? sample = await st.read(key: "something");
    if(sample != null) {
      setState(() {
        _email_controller.text = sample;
      });
    }
  }


  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: new SafeArea(child: _buildLoginPage(context)),
    );
  }

  Widget _buildLoginPage(BuildContext context) {

    return Center(
        child: Column(
            children: <Widget>[
                TextField(
                inputType: TextInputType.emailAddress,
                controller: _email_controller,
                ),
            ]
        )
    );
  }
}