ReadFileWithClosure.swift

func load(from url: URL, completion: @escaping (Result<Data, Error>) -> Void) {
    DispatchQueue.global().async {
        do {
            let data = try Data(contentsOf: url)
            DispatchQueue.main.async {
                completion(.success(data))
            }
        } catch {
            DispatchQueue.main.async {
                completion(.failure(error))
            }
        }
    }
}