To deploy a Go site, there are some components that have to be uploaded to the server. By using Webmin the uploading gets simpler. Basically the deployment is three steps.
Test locally on your computer first. In order to check that everything works as expected.
Upload the files to the server (Using Webmin). This part is "drag-and-drop" to the corresponding folders on the server.
Start the Go server. Debian has a service called systemd that can start, restart and monitor the status and automatically restart the Go server if needed.
I have not yet investigated using Github or similar for this process. But I assume it is possible.