[SOLVED] Technical question on how this application starts up

In brief:
- User goes to Mattermost
- The go code serves the static root.html.
- The web browser requests the additional assets listed in root.html.
- One of those JavaScript assets (https://github.com/mattermost/platform/blob/master/webapp/root.jsx#L85) has registered the window.setup_root() function which is then executed automatically by the web browser because of the <script> tags.
- The JavaScript webapp takes over from here.