https://github.com/mattermost/mattermost-server
https://github.com/getfider/fider
https://github.com/ketchuphq/ketchup
https://github.com/mantishk/galore
https://gitlab.com/NebulousLabs/Sia
https://github.com/netlify/gocommerce
https://github.com/ponzu-cms/ponzu
This is a list of webapps written in go. I didn't check the source and can't guarantee it's good quality