I understand you can use index inside range:
{{range $i, $e := .First}}$e - {{index $.Second $i}}{{end}}
From: how to use index inside range in html/template to iterate through parallel arrays?
How do I range over the index if it also contains an array?
Eg.
type a struct {
Title []string
Article [][]string
}
IndexTmpl.ExecuteTemplate(w, "index.html", a)
index.html
{{range $i, $a := .Title}}
{{index $.Article $i}} // Want to range over this.
{{end}}