router.go
func (r *Router) Group(pattern string, group func(*Router)) {
	c := r.pattern(pattern)
	group(r.clone(c))
}
func (r *Router) Group(pattern string, group func(*Router)) {
	c := r.pattern(pattern)
	group(r.clone(c))
}
func ( r * Router ) Group ( pattern string , group func ( * Router ) ) { c := r . pattern ( pattern ) group ( r . clone ( c ) ) }
// Group calls the specified function with the subrouter for the given pattern
Group calls the specified function with the subrouter for the given pattern