server.go
func (hm HandlerMap) Merge(other HandlerMap) {
	for key, methods := range other {
		if _, ok := hm[key]; !ok {
			hm[key] = map[string]Builder{}
		}
		for method, builder := range methods {
			hm[key][method] = builder
		}
	}
}
func (hm HandlerMap) Merge(other HandlerMap) {
	for key, methods := range other {
		if _, ok := hm[key]; !ok {
			hm[key] = map[string]Builder{}
		}
		for method, builder := range methods {
			hm[key][method] = builder
		}
	}
}
// Merge merges another HandlerMap into itself.