//header.tmpl
{{define "header"}}
<html>
<head>
    <title>Something here</title>
</head>
<body>
  {{end}}

//content.tmpl
{{define "content"}}
{{template "header"}}
<h1>Nested here</h1>
<ul>
    <li>Nested usag</li>
    <li>Call template</li>
</ul>
{{template "footer"}}
{{end}}

//footer.tmpl
{{define "footer"}}
</body>
</html>
{{end}}
