SwiftConcurrency_AnIntroduction_ErrorProneCode.swift

func fetchData(from url: URL, withCompletion completion: @escaping (Result<ModelWrapper, Error>) -> Void) -> Void {

        let firstTask = URLSession.shared.dataTask(with: url) { data, response, error in

            if let error = error {
                completion(.failure(error))
                // 😱 DID NOT RETURN!
            }

            guard let data = data else {
                completion(.failure(APIErrors.requestError))
                return
            }

            guard let model = try? JSONDecoder().decode(Model.self, from: data) else {
                // 😱 DID NOT CALL COMPLETION HANDLER!
                return
            }

            let imageUrl = model.imageURL
            let secondTask = URLSession.shared.dataTask(with: imageUrl) { data, response, error in

                // 😱 PYRAMID OF DOOM STARTING TO FORM!
                if let error = error {
                    completion(.failure(error))
                    return
                }

                guard let data = data else {
                    completion(.failure(APIErrors.imageRequestError))
                    return
                }

                guard let image = UIImage(data: data) else {
                    // 😱 DID NOT CALL COMPLETION HANDLER!
                    return
                }

                let modelWrapper = ModelWrapper(model: model, image: image)
                completion(.success(modelWrapper))
            }

            secondTask.resume()
        }

        firstTask.resume()
    }