title: Why response.body() its null?
body: <p>Im using retrofit to send a a json object to the server, im trying to create a user, im sending this json object
  <code>{"apellido":"prueba","email":"prueba@hotmail.com","fechaDeNacimiento":"11/29/1998","formaDeRegistro":"Android","nombre":"prueba","password":"12345678","username":"prueba"}</code></p>
  
  <p>In this example i create a invalid user , so the server response with a json object where code its the code error and message its the explication of the error</p>
  
  <pre><code>[{"code":"5","message":"The email is in use"}]
  </code></pre>
  
  <p>Interface</p>
  
  <pre><code>public interface UserClient {
  
  
  @POST("usuarios")
  Call&lt;Usuarios&gt; create(@Body Usuarios usuario);
  </code></pre>
  
  <p>}</p>
  
  <p>Data model</p>
  
  <pre><code>import com.google.gson.annotations.SerializedName;
  public class Usuarios {
  
  @SerializedName("username")
  String username;
  @SerializedName("email")
  String email;
  @SerializedName("password")
  String password;
  @SerializedName("nombre")
  String nombre;
  @SerializedName("apellido")
  String apellido;
  @SerializedName("fechaDeNacimiento")
  String fechaDeNacimiento;
  @SerializedName("formaDeRegistro")
  String formaDeRegistro;
  
   String message;
  
  
  public Usuarios(String email, String username, String password, String nombre, String apellido, String fechaDeNacimiento, String formaDeRegistro){
      this.username=username;
      this.email=email;
      this.password=password;
      this.nombre = nombre;
      this.apellido= apellido;
      this.fechaDeNacimiento = fechaDeNacimiento;
      this.formaDeRegistro = formaDeRegistro;
  }
  
  public String getMessage(){
      return message;
  }
  </code></pre>
  
  <p>}</p>
  
  <p>and Retrofit implement </p>
  
  <pre><code> OkHttpClient.Builder okhttpClientBuilder=new OkHttpClient.Builder();
      HttpLoggingInterceptor loggin=new HttpLoggingInterceptor();
      loggin.setLevel(HttpLoggingInterceptor.Level.BODY);
      okhttpClientBuilder.addInterceptor(loggin);
      Retrofit.Builder builder = new Retrofit.Builder()
              .baseUrl("https://intense-lake-39874.herokuapp.com")
              .addConverterFactory(GsonConverterFactory.create())
              .client(okhttpClientBuilder.build());
  
      Retrofit retrofit = builder.build();
  
  
      UserClient service = retrofit.create(UserClient.class);
      Call&lt;Usuarios&gt; call = service.create(usuario);
  
      call.enqueue(new Callback&lt;Usuarios&gt;() {
          @Override
          public void onResponse(Call&lt;Usuarios&gt; call, Response&lt;Usuarios&gt; response) {
  
              Toast.makeText(Main2Activity.this,"Usuario Registrado! "+response.body().getMessage,Toast.LENGTH_SHORT).show();
  
          }
  
          @Override
          public void onFailure(Call&lt;Usuarios&gt; call, Throwable t) {
                  Toast.makeText(Main2Activity.this,"Algo fallo..",Toast.LENGTH_SHORT).show();
  
          }
      });
  }
  </code></pre>
  
  <p>So  i can see the logcat response but in the body its appoint to null, how i can acces to the "message"?</p>
  
  <p><a href="https://i.stack.imgur.com/3pMwc.png" rel="nofollow noreferrer">This is the logcat</a></p>