Retrofit + Gson can not parse simple Map

I have a JSON as follows

{
  "1.2.3.4": "domain1.com",
  "1.2.3.5": "domain2.com"
}

And a model

public class DnsLookup {
  @Getter @Setter private Map<String, String> entry;
}

And retrofit query interface

  @GET("/dns/")
  Call<DnsLookup> getDns(@QueryMap Map<String, String> params);

When I make the query, I get null in dns.

    Call<DnsLookup> call = service.getDns(queryMap);
    Response<DnsLookup> response;
    response = call.execute();
    var dns = response.body();

Actually the original JSON is

{
  "1.2.3.4": [
    "domain1.com", "domain1-1.com"
  ],
  "1.2.3.5": [
    "domain2.com"
  ]
}

And I have tried the following model to only get null. Since the following didn't work, I broke the problem to just key-value pairs. To my surprise, the simple map also didn't work.

public class DnsLookup {
  @Getter @Setter private Map<String, List<String>> entry;
}

Am I doing a noob mistake?

Use:

@GET("/dns/")
Call<Map<String, List<String>>> getDns(@QueryMap Map<String, String> params);

Instead of:

@GET("/dns/")
Call<DnsLookup> getDns(@QueryMap Map<String, String> params);