core/templates/layout/breadcrumb.html.tpl

{{define "breadcrumb"}}
<nav aria-label="breadcrumb">
  <ol class="breadcrumb">
    {{$data:=.}}
    {{range $i,$el := .}}
    {{if ($i|mod2)}}
    {{$url:=index $data ($i|incr)}}
    {{if eq $url "current"}}
    <li class="breadcrumb-item active" aria-current="page">{{$el}}</li>
    {{else}}
    <li class="breadcrumb-item"><a href="{{$url}}">{{$el}}</a></li>
    {{end}}
    {{end}}
    {{end}}
  </ol>
</nav>
{{end}}