I use embed to embed all assets in the binary itself. "go build" and then "scp" the binary to the production server and "systemctl restart appserver"
Regarding the original question we use fiber.io for a few systems and have loved it’s capabilities and performance.
How do you like the template package ? Can you compare it to Jinja/Twig ?
Overall, I find Go's template system to be a bit clunky but it certainly gets the job done. The template system is fairly minimal so it feels mostly like working with HTML, but it gives you a few tools to use.. mainly passing data down the template/sub-templates and the ability to define template functions/helpers. Minimal... but it's all you really need.
I converted my business from Rails 5 to Go about a year ago and the ERB was fairly straight forward to convert to Go's template system.. it felt like I was mostly converting <% .. %> to {{ .. }} and changing <%= render ... %> to {{ template ... }}
For the database I use Postgresql with the standard library's database/sql package (using lib/pq as the driver).
For scheduled emails and tasks, I store them in Postgres and I have a task that is run through my server binary every few hours (ex: "server --task scheduled-tasks").