Update index.md (#7070)

Added a brief description of realtime communication, methods of achieving it and a link to a YouTube video showing websockets being used with Go.

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Co-authored-by: dsh <daniel.s.holdsworth@gmail.com>

src/data/roadmaps/golang/content/106-go-realtime-communication/index.md

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 # Go realtime communication
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+## What is real-time communication?
+Just as it says in the name, real-time communication is the handling of requests concurrently and efficiently. Whether it is a chat/messaging app, an email service, a game server or any collaborative online project (for example, Excalidraw), there are a few different ways of handling real-time communication, but the most common is through the use of WebSockets. Other options for handling real-time communications include MQTT protocol and server-sent events, among others.
+
+Learn more from the following resources:
+
+- [@video@Golang websocket](https://youtu.be/G8SKhZMqvsE)