将通用结构/接口传递给函数并返回

Can I pass a generic struct or interface into a function, and then return it? I've tried using pointers in the example below, and I've also tried using struct as a return type but I can't seem to do it.

If I use interface{} instead, I seem to be able to pass postData in but getting it back seems to be impossible by returning or updating a pointer. Can anyone tell me where I'm going wrong?

func EmailHandler(writer http.ResponseWriter, request *http.Request) {
    var postData = EmailPostData{}
    ConvertRequestJsonToJson(request, &postData)
}

func ConvertRequestJsonToJson(request *http.Request, model *struct{}) {
    postContent, _ := ioutil.ReadAll(request.Body)
    json.Unmarshal([]byte(postContent), &model)
}

func EmailHandler(writer http.ResponseWriter, request *http.Request) {
    var postData = EmailPostData{}
    ConvertRequestJsonToJson(request, &postData)
    //Use postData, it should be filled
}
func ConvertRequestJsonToJson(request *http.Request, model interface{}) {
    postContent, _ := ioutil.ReadAll(request.Body)
    json.Unmarshal([]byte(postContent), model)//json.Unmarshal stores the result in the value pointed to by model
}