router.go
func (r *Router) Host(hosts ...string) *Router {
	c := r.route.clone()
	c.Hosts = hosts
	return r.clone(c)
}
func (r *Router) Host(hosts ...string) *Router {
	c := r.route.clone()
	c.Hosts = hosts
	return r.clone(c)
}
func ( r * Router ) Host ( hosts ... string ) * Router { c := r . route . clone ( ) c . Hosts = hosts return r . clone ( c ) }
// Host lets you specify the host(s) the route is available for
Host lets you specify the host ( s ) the route is available for