public ClientFactoryBuilder proxyConfig(ProxyConfig proxyConfig) {
        requireNonNull(proxyConfig, "proxyConfig");
        option(ClientFactoryOptions.PROXY_CONFIG_SELECTOR, ProxyConfigSelector.of(proxyConfig));
        return this;
    }
Sets the {@link ProxyConfig} which contains proxy related configuration.
core/src/main/java/com/linecorp/armeria/client/ClientFactoryBuilder.java