Minimizing Goagent requires clicking its system-tray icon, which is rather inconvenient.
Here's a way to make it minimize automatically when it opens.
Open proxy.ini and change:
visible = 1
to:
visible = 0
Restart it and you'll see the result!

To run it at startup, put a shortcut in the Start menu's Startup folder.
Administrator privileges are needed only the first time, to install the SSL certificate. After that, it works without them.