title: How to serialize GeoPoint using dart json_serializable package
body: <p>I am trying to filter my Firestore collections by distance using the following package.</p>
  
  <p><a href="https://github.com/fluttercommunity/firestore_helpers" rel="nofollow noreferrer">https://github.com/fluttercommunity/firestore_helpers</a></p>
  
  <p>Referring to their example they are using jaguar_serializer to convert the data received from Firestore to Location class. I have implement their getDataInArea function in my app but I am currently stuck because I am using json_serializable.</p>
  
  <p>I have looked around and found that there is a suggestion on how to handle GeoPoint if using built_value at the following link.</p>
  
  <p><a href="https://github.com/google/built_value.dart/issues/417#issuecomment-391661750" rel="nofollow noreferrer">https://github.com/google/built_value.dart/issues/417#issuecomment-391661750</a></p>
  
  <p>So I am wondering is there a way to implement something like what is shown in jaguar_serializer and built_value but using json_serializable package instead.</p>
  
  <p>I am guessing that one way is to use <code>@JsonKey(fromJson: , toJson: )</code> but I am not too sure about how to get about doing it.</p>