How to add new methods to an existing type in Go?

Question

I want to add a convenience util method on to gorilla/mux Route and Router types:

package util

import(
    \"net/http\"
    \"github.com/0xor1/         


        

Answer 1

As the compiler mentions, you can't extend existing types in another package. You can define your own alias or sub-package as follows:

type MyRouter mux.Router

func (m *MyRouter) F() { ... }

or by embedding the original router:

type MyRouter struct {
    *mux.Router
}

func (m *MyRouter) F() { ... }

...
r := &MyRouter{router}
r.F()