interface GenericAsyncCallback<E, T> {
    (err: E | null, ...results: T[]): void
}

const asyncApi = (callback: GenericAsyncCallback<Error, number>) => {
    setTimeout(() => {
        const error = Math.random() > 0.5 ? new Error(`Connection Timeout`) : null;

        if (error) callback(error);
        else callback(null, Date.now());
    }, 1000);
}