render.go
func (render *Render) RegisterFuncMap(name string, fc interface{}) {
	if render.funcMaps == nil {
		render.funcMaps = template.FuncMap{}
	}
	render.funcMaps[name] = fc
}
func (render *Render) RegisterFuncMap(name string, fc interface{}) {
	if render.funcMaps == nil {
		render.funcMaps = template.FuncMap{}
	}
	render.funcMaps[name] = fc
}
// RegisterFuncMap register FuncMap for render.