Auto re-send call invitation after call timeout

///    Declare variables that you need to use, and make sure to manage their lifecycles
  const maxRetryCount = 2;
  final Map calleesRetryCount = {};

  ///    Listen to the onOutgoingCallTimeout during initialization.
  ZegoUIKitPrebuiltCallInvitationService().init(
    appID: YourAppID,
    appSign: YourAppSign,
    userID: userID,
    userName: userName,
    plugins: [ZegoUIKitSignalingPlugin()],
    invitationEvents: ZegoUIKitPrebuiltCallInvitationEvents(
      onOutgoingCallTimeout: (
          String callID,
          List callees,
          bool isVideoCall,
          ) async {
        ///  Set the maximum retry count. If it exceeds, no more call invitations will be sent.
        final retryCount = calleesRetryCount[callID] ?? 0;
        if (retryCount >= maxRetryCount) {
          calleesRetryCount.remove(callID);
          return;
        }

        calleesRetryCount[callID] = retryCount + 1;

        ///  Re-send call invitation
        await ZegoUIKitPrebuiltCallController().invitation.send(
          callID: callID,
          invitees: callees
              .map((callee) => ZegoCallUser(callee.id, 'user_${callee.id}'))
              .toList(),
          isVideoCall: isVideoCall,
        );
      },
    ),
  );