public final HttpAsyncClientBuilder setIoReactorExceptionCallback(final Callback<Exception> ioReactorExceptionCallback) {
        this.ioReactorExceptionCallback = ioReactorExceptionCallback;
        return this;
    }
Sets the callback that will be invoked when the client's IOReactor encounters an uncaught exception.

@return this instance.
@since 5.1
httpclient5/src/main/java/org/apache/hc/client5/http/impl/async/HttpAsyncClientBuilder.java