app/ios/Runner/AppDelegate.swift

import UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    GeneratedPluginRegistrant.register(with: self)
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
  func connectionShouldUseCredentialStorage(_ connection: NSURLConnection) -> Bool {
          return true
      }

      func connection(_ connection: NSURLConnection, willSendRequestFor challenge: URLAuthenticationChallenge) {
          if let previous = challenge.previousFailureCount as? ssize_t {
              print(String(format: "didReceiveAuthenticationChallenge %@ %zd", challenge.protectionSpace.authenticationMethod, previous))
          }
          if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust {
              challenge.sender?.use(URLCredential(for: challenge.protectionSpace.serverTrust), for: challenge)
              challenge.sender?.continueWithoutCredential(for: challenge)
          }
      }

      func connection(_ connection: NSURLConnection, canAuthenticateAgainstProtectionSpace protectionSpace: URLProtectionSpace) -> Bool {
          return protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust
      }
}