// HTTP服务执行入口
func (s *Server) ServeHTTP(r engine.Request, w engine.Response) {
var h *echo.Echo
app, ok := s.Apps[r.Host()]
if !ok || app.Handler == nil {
h = s.Core
} else {
h = app.Handler
}
if h != nil {
h.ServeHTTP(r, w)
} else {
w.NotFound()
}
}
