my-site/layouts/sitemap.xml

<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
  xmlns:xhtml="http://www.w3.org/1999/xhtml">
  {{ range .Data.Pages }}{{ if ne .Params.sitemap_exclude true }}
  <url>
    <loc>{{ .Permalink }}</loc>{{ if not .Lastmod.IsZero }}
    <lastmod>{{ safeHTML ( .Lastmod.Format "2006-01-02T15:04:05-07:00" ) }}</lastmod>{{ end }}{{ with .Sitemap.ChangeFreq }}
    <changefreq>{{ . }}</changefreq>{{ end }}{{ if ge .Sitemap.Priority 0.0 }}
    <priority>{{ .Sitemap.Priority }}</priority>{{ end }}{{ if .IsTranslated }}{{ range .Translations }}
    <xhtml:link
                rel="alternate"
                hreflang="{{ .Lang }}"
                href="{{ .Permalink }}"
                />{{ end }}
    <xhtml:link
                rel="alternate"
                hreflang="{{ .Lang }}"
                href="{{ .Permalink }}"
                />{{ end }}
  </url>
  {{ end }}{{ end }}
</urlset>