{{- $canonical := .Permalink -}}

{{- with .Site.Params.site.canonical -}}
  {{- $canonical = print $.Site.Params.site.canonical $.RelPermalink -}}
{{- end -}}

{{- with .Params.feed -}}
  {{- $canonical = $.Params.feed.link -}}
{{- end -}}

{{- with .Params.canonical -}}
  {{- $canonical = $.Params.canonical -}}
{{- end -}}

 <link rel="canonical" href="{{ $canonical }}" />