convert struct pointer to interface{}

To turn *foo into an interface{} is trivial:

f := &foo{}
bar(f) // every type implements interface{}. Nothing special required

In order to get back to a *foo, you can either do a type assertion:

func bar(baz interface{}) {
    f, ok := baz.(*foo)
    if !ok {
        // baz was not of type *foo. The assertion failed
    }

    // f is of type *foo
}

Or a type switch (similar, but useful if baz can be multiple types):

func bar(baz interface{}) {
    switch f := baz.(type) {
    case *foo: // f is of type *foo
    default: // f is some other type
    }
}