@Override
    public void close(final CloseMode closeMode) {
        if (closed.compareAndSet(false, true)) {
            perRouteCache.clear();
            pool.close(closeMode);
        }
    }
Experimental connections pool implementation that acts as a caching facade in front of
a standard {@link ManagedConnPool} and shares already leased connections to multiplex
message exchanges over active HTTP/2 connections.
@param <T> route
@param <C> connection object

@since 5.5
httpclient5/src/main/java/org/apache/hc/client5/http/impl/nio/H2SharingConnPool.java