export declare class Selector<T extends Array<() => PromiseLike<U>>, U> {
    private readonly _Generators;
    private readonly _Futures;
    constructor(_Generators: T);
    next(): Promise<Awaited<ReturnType<T[number]>>>;
    static addIndex<T>(generator: () => PromiseLike<T>, index: number): Promise<[T, number]>;
}