public final HttpAsyncClientBuilder setDefaultRequestConfig(final RequestConfig config) {
        this.defaultRequestConfig = config;
        return this;
    }
Sets default {@link RequestConfig} instance which will be used
for request execution if not explicitly set in the client execution
context.

@return this instance.
httpclient5/src/main/java/org/apache/hc/client5/http/impl/async/HttpAsyncClientBuilder.java