Comment 1:

In the cases whose behaviour you want to be different, you are passing in a pointer to
an interface{}.  The encoding/json docs describe how JSON is unmarshaled into an
interface value, and that is what you are seeing.  So this is behaving correctly
according to the package docs.
I agree that this makes it hard to decode into a slice created by reflect.MakeSlice.  I
think you'll have to walk the map and assign to the slice using the reflect methods.  At
least, I don't immediately see another way to do it.

Status changed to WorkingAsIntended.

Comment 2 by emanuelpalm:

Alright. Thank you for your time.
By the way, I would like to see some decoder/encoder for transforming to and from struct
<-> map[string]interface{} in the standard lib. That would have helped me out.