Solution for Generic in Go - json

Question

I want to make a useful library for JSON responses. In Java I've this already. I started now new with Go and have no idea how to transform my Java code. I've read that Go doesn't have anything like generics, but how can I solve my problem?
I'm talking about the following part of code:
#Data
public class ServiceResult<T extends Serializable> implements Serializable {
private ServiceResultStatus status;
private String type;
private T content;
private String hash;
private String destination;
private HashMap<String, Metadata> metadata = new HashMap<>();
...
The idea of service-result is to provide an structural pattern for RESTful web services. If you need more information, here is the link to my repo on Github: https://github.com/Viascom/service-result
A service-result looks at the end like this:
{
"status": "successful",
"type": "ch.viascom.example.models.response.GetTasksResponse",
"content": [
{
"id": "3e99c7fb-0ed7-11e7-a7a5-0050569c3e5a",
"name": "Example Task"
}
],
"hash": "7bf9c04d1e9f8fe7995e4b8beeac1a4c830e7ea",
"destination": "ch.viascom.example.handler.TaskHandler",
"metadata": {
}
}

Answer 1

You can add the json-mapping directly to the structure definition and use the encoder, decoder to marshal and unmarshal it. It's all built in and easier than in other languages, imho.
type ServiceResponse struct {
Value string`json:"nameInJsonResponse"`
}
here is a good example from the playground: https://play.golang.org/p/4L2wMVv7tW
For your particular case it should be something like this:
type ServiceResult struct {
Status ServiceResultStatus`json:"status"`
Type string`json:"type"`
Hash string`json:"hash"`
Destination string`json:"destination"`
Metadata map[string]Metadata metadata`json:"metadata"`
}
type ExplizitServiceResult struct {
ServiceResult
Content SomeStruct`json:"content"`
}
https://play.golang.org/p/FFfiq6LxVt
If you don't want to derive every user struct from the ServiceResult you can define the content as interface{} so every struct can be inserted. I've updated my example for this. Maybe this is the easiest solution to your problem.
https://play.golang.org/p/LNgreqrnnw