Populate template map in Go

populate_templates.go

func populateTemplates(fm template.FuncMap) map[string]*template.Template {
	result := make(map[string]*template.Template)
	const basePath = "templates"
	layout := template.Must(template.ParseFiles(basePath + "/_layout.html")).Funcs(fm)
	dir, err := os.Open(basePath + "/content")
	if err != nil {
		panic("failed to open template base directory: " + err.Error())
	}
	defer dir.Close()
	fis, err := dir.Readdir(-1)
	if err != nil {
		panic("failed to contents of content directory: " + err.Error())
	}
	for _, fi := range fis {
		f, err := os.Open(basePath + "/content/" + fi.Name())
		if err != nil {
			panic("failed to open template '" + fi.Name() + "': " + err.Error())
		}
		content, err := ioutil.ReadAll(f)
		if err != nil {
			panic("failed to read content from file '" + fi.Name() + "': " + err.Error())
		}
		_ = f.Close()
		tmpl := template.Must(layout.Clone())
		_, err = tmpl.Parse(string(content))
		if err != nil {
			panic("failed to parse contents of file '" + fi.Name() + "': " + err.Error())
		}
		result[fi.Name()] = tmpl
	}
	return result
}