enum NetworkRequestError: Error {
    case hostNotAvailable
    case accountNotAvailable

    func finish<T>() -> Result<T, NetworkRequestError> {
        return .failure(self)
    }
}

func fetch(result: @escaping (Result<(any: [Any], any1: [Any]), NetworkRequestError>) -> Void) {
    guard host != nil else {
        result(NetworkRequestError.hostNotAvailable.finish())
        return
    }

    ...
}

enum NetworkRequestError: Error {
    case hostNotAvailable
    case accountNotAvailable
}

func fetch(result: @escaping (Result<(any: [Any], any1: [Any]), NetworkRequestError>) -> Void) {
    guard host != nil else {
        result(.failure(.hostNotAvailable))
        return
    }

    ...
}