You may need this side-by-side as a start: template package - text/template - Go Packages. Template functions can be slightly different. For some (e.g. strings processing), you may need to port the strings functions before using the template file.
compare equal is:
{{ if eq 1 1 }}
Not a rule but the practice would be: .html.tmpl or .html.template. The first denotes the output extension while the second denotes it is a template.
If confused, stick to .tmpl as standard HTML does not interpret go template codes.