You can start with getting the right amount of right brackets – but that error doesn’t match with the error you get, which tells me this example is incomplete/not exact.
A reproduce-able GitHub repo is best, but it should at least be the real deal.
The error message could be better, but the .Params in this case is a slice and cannot be indexed by a string. Params could also be a map (named params), but in your case there isn’t any params in use, so it defaults to slice.
The <!-- comments have no real effect on Go template code, btw.