You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: gee.go
    path of file: ./repos/7days-golang/gee-web/day4-group/gee
    
    the code of the file until where you have to start completion: package gee

import (
	"log"
	"net/http"
)

// HandlerFunc defines the request handler used by gee
type HandlerFunc func(*Context)

// Engine implement the interfa
    
func (group *RouterGroup) Group(prefix string) *RouterGroup {
	engine := group.engine
	newGroup := &RouterGroup{
		prefix: group.prefix + prefix,
		parent: group,
		engine: engine,
	}
	engine.groups = append(engine.groups, newGroup)
	return newGroup
}