For Prometheus's console templates (basically offering a html templating engine to end users to create monitoring consoles with), I used Go's own templating language as nothing else seemed mature at the time.

Go is strongly typed, and so is it's templating language. This means that you need to take a much more rigorous approach to using them, as a single unhandled edge case value can break the entire page. Contrast this with something like Jinja2 where if you mess up it'll only break a small bit of the page.

I managed to produce a usable template system, but it's still a tad more verbose than I'd like. It'd have been nice if a more scripting-language style templating language had been an option.