Simple RxSwift's usage of Single for async network events

GitHubAPISingle.swift

enum GitHubAPIError: Error {
    case userIsEmpty
    case invalidData
}

func fetchGithubUser(_ user: String) -> Single<[String: Any]> {
    guard user.isEmpty == false else { return Single.error(GitHubAPIError.userIsEmpty) }
    return Single<[String: Any]>.create(subscribe: { completion in
        let task = URLSession.shared
            .dataTask(with: URLRequest(url: URL(string: "https://api.github.com/users/\(user)")!), completionHandler: { data, _, error in
                if let error = error { return completion(.error(error)) }

                guard let data = data,
                    let json = try? JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String: Any] else {
                    return completion(.error(GitHubAPIError.invalidData))
                }

                return completion(.success(json))
            })

        task.resume()

        return Disposables.create {
            task.cancel()
        }
    })
}

fetchGithubUser("vinhnx").subscribe { event in
    switch event {
    case .success(let response):
        print(response)
    case .error(let failure):
        print(failure)
    }
}