Retrofit, callback for 204 No Content response?

This is the kotlin way for the implementation to deal with HTTP 204 and no content.

@DELETE(USER_API_BASE_URL + "/{id}")
suspend fun deleteuser(@HeaderMap headers: Map<String, String>, 
                       @Path("id") id: String)
: Response<Void>

The solution was pointed out by Jake Wharton in the comments. Use ResponseCallback.

EDIT: this response is no longer valid for Retrofit < 2.

Retrofit 2.x no longer has a ResponseCallback as mentioned in the other answer. You want to use a Response<Void> type.

The RxJava declaration:

@PUT Observable<Response<Void>> foo();

The standard declaration:

@PUT Call<Response<Void>> bar();