How to index a slice element?
Use the index command like so:
{{index .Keys 3}}
As stated in the html/template package, the majority of examples are actually located in the text/template pkg docs. See http://golang.org/pkg/text/template/
From the docs
index
Returns the result of indexing its first argument by the
following arguments. Thus "index x 1 2 3" is, in Go syntax,
x[1][2][3]. Each indexed item must be a map, slice, or array.