public static CloseableHttpAsyncClient createFileBound(final File cacheDir) {
        return CachingHttpAsyncClientBuilder.create().setCacheDir(cacheDir).build();
    }
Creates {@link CloseableHttpAsyncClient} instance that uses a file system
bound response cache.

@param cacheDir location of response cache.
httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/CachingHttpAsyncClients.java