Unexpected nil value when configuring flutter_config_plus package in AppDelegate.swift

[Mahm0ud-Ahmed]

Issue Description: Unexpected nil value when configuring flutter_config_plus package in AppDelegate.swift

Steps to Reproduce:

Integrate the flutter_config_plus package into a Flutter project.
Open the AppDelegate.swift file.
Configure the package by adding the necessary code as instructed in the package documentation.
Run the project on iOS.
Expected Behavior:

The flutter_config_plus package should be successfully configured, and the necessary values should be retrieved from the configuration file or environment variables.

Actual Behavior:

Upon running the project on iOS, a fatal error is encountered with the following error message:

Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value: file Runner/AppDelegate.swift, line 13

Additional Information:

The error occurs on line 13 of the AppDelegate.swift file where the FlutterConfigPlusPlugin.env(for: "IOS_GOOGLE_MAP_API_KEY") method is called.
The IOS_GOOGLE_MAP_API_KEY is an environment variable set for the project, and it is expected to provide the necessary API key for Google Maps.
The error suggests that the optional value returned by FlutterConfigPlusPlugin.env(for:) is nil and is being force-unwrapped, resulting in the crash.

AppDelegate.swift file

import UIKit
import Flutter
import GoogleMaps
import flutter_config_plus

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    GMSServices.provideAPIKey(FlutterConfigPlusPlugin.env(for: "IOS_GOOGLE_MAP_API_KEY"));
    GeneratedPluginRegistrant.register(with: self)
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}

[stevennguyenn]

Did you setup release.xcconfig or debug.xcconfigfile ?