func MongoContext(txn bool) (mongo.SessionContext, error) {
	var mctx mongo.SessionContext
	if !txn {
		return mctx, nil
	}

	sess, err := client.StartSession()
	if err != nil {
		return nil, err
	}

	err = sess.StartTransaction()
	if err != nil {
		return nil, err
	}

	_ = mongo.WithSession(context.Background(), sess, func(sessionContext mongo.SessionContext) error {
		mctx = sessionContext
		return nil
	})

	return mctx, nil
}

func ErrorExample(ctx context.Context, in *pb.Mock) (res MockResponse, err error) {
	mctx, err := MongoContext(true)
	if err != nil {
		return
	}

	params, ok := metadata.FromIncomingContext(ctx)
	if !ok {
		return
	}

	var wg sync.WaitGroup
	var err1, err2, err3 error

	wg.Add(1)
	go func() {
		defer wg.Done()
		_, err1 = collection1.SomeOperation(mctx, params)
	}()

	wg.Add(1)
	go func() {
		defer wg.Done()
		_, err2 = collection2.SomeOperation(mctx, params)
	}()

	wg.Add(1)
	go func() {
		defer wg.Done()
		_, err3 = collection3.SomeOperation(mctx, params)
	}()

	wg.Wait()

	if err1 != nil {
		return res, err1
	}
	if err2 != nil {
		return res, err2
	}
	if err3 != nil {
		return res, err3
	}

	err = mctx.CommitTransaction(context.Background())
	if err != nil {
		return
	}

	return &MockResponse{
		Success: true,
	}, nil
}

func WorkaroundExmaple(ctx context.Context, in *pb.Mock) (res MockResponse, err error) {
	mctx, err := MongoContext(true)
	if err != nil {
		return
	}

	params, ok := metadata.FromIncomingContext(ctx)
	if !ok {
		return
	}

	_, err = collection1.SomeOperation(mctx, params)
	if err != nil {
		return
	}

	var wg sync.WaitGroup
	var err1, err2 error

	wg.Add(1)
	go func() {
		defer wg.Done()
		_, err1 = collection2.SomeOperation(mctx, params)
	}()

	wg.Add(1)
	go func() {
		defer wg.Done()
		_, err2 = collection3.SomeOperation(mctx, params)
	}()

	wg.Wait()

	if err1 != nil {
		return res, err1
	}
	if err2 != nil {
		return res, err2
	}

	err = mctx.CommitTransaction(context.Background())
	if err != nil {
		return
	}

	return &MockResponse{
		Success: true,
	}, nil
}