如何在通用函数中解码json

How do I do something like this (assuming T is a template like in C++, C#, Java etc...) in golang:

func DecodeFormToJson(r *http.Request, t *T) err error {
    decoder := json.NewDecoder(r.Body)
    err = decoder.Decode(&t)
    return 
}

Simply using an interface{} which is what Decoder.Decode uses anyway, for example:

func proxyDecode(r io.Reader, i interface{}) error {
    dec := json.NewDecoder(r)
    return dec.Decode(i)
}