Gin IRouter.Group(string, ...HandlerFunc) *RouterGroup should return IRouter

Description

IRouter interface should return IRouter on the Group function to allow other implementations of IRouter.

Expectations

type IRouter interface {
    IRoutes
    Group(string, ...HandlerFunc) IRouter
}

Actual result

type IRouter interface {
    IRoutes
    Group(string, ...HandlerFunc) *GroupRouter
}

Environment

• gin version (or commit ref): 1.9.0