/**
 * Barrier is a one-time signal that can be used in like ready states, close events etc.
 *
 * it's basically a special type of promise with no resolve value and will never reject.
 *
 * @example
 * ```
 * const serverReady = new Barrier()
 * server.on('listening', () => barrier.unlock())
 * await serverReady
 * ```
 *
 * @public
 */
export declare class Barrier implements PromiseLike<void> {
    private future;
    constructor();
    unlock(): void;
    get unlocked(): boolean;
    then<TResult1 = void, TResult2 = never>(onfulfilled?: (() => TResult1 | PromiseLike<TResult1>) | null | undefined, onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined): PromiseLike<TResult1 | TResult2>;
}
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