@UnstableApi
    default SELF selectionTimeout(Duration selectionTimeout) {
        requireNonNull(selectionTimeout, "selectionTimeout");
        checkArgument(!selectionTimeout.isNegative(), "selectionTimeout: %s (expected: >= 0)",
                      selectionTimeout);
        return selectionTimeoutMillis(selectionTimeout.toMillis());
    }
Sets the timeout to wait until a successful {@link Endpoint} selection.
{@link Duration#ZERO} disables the timeout.
If unspecified, {@link Flags#defaultConnectTimeoutMillis()} is used by default.
core/src/main/java/com/linecorp/armeria/client/endpoint/DynamicEndpointGroupSetters.java