Method to get main handler is desired

[collinmsn]

It's convenient to get request handler name by gin.Context.HandlerName, but it not always work well. In case that handler is installed with decorator wrapped, HanderName will return func1, which is meaningless.
r.GET("/foo", Decorator(Foo))
Since there's no way to get function name of wrapped func, it can resort to user passing this value explicitly. Something like r.GETEX("/foo", Decorator(Foo), "Foo")

Then I can save function point to name map on handler register and get handler name in middleware,
as long as I can get FuncHandler with ctx.

So it's desired to add a method to return main handler.