Update to architecture doc

README.md

@@ -4,6 +4,11 @@ Learning MQTT with Golang by doing. This repo is a simple example of using a Gol
 
 1883, Eclipse Mosquitto unsecured (opening the port on the internet is not recommended).
 
+
+## Architecture
+
+![mqtt-arch](./img/mqtt-architecture.svg)
+
 ## Development
 
 For local development we use [Mosquitto](https://mosquitto.org/) as our MQTT broker, with TLS enabled.