Implement both JsonMarshaler and JsonUnmarshaler

If a type only defines one-half of the symmetry (e.g. it implements MarshalJSON() but not UnmarshalJSON() ), then that type doesn't satisfy the codec encoding/decoding check and instead codec will not encode or decode the item using the special interface methods.

util/data/data.go

@@ -77,6 +77,10 @@ func (d *Doc) MarshalJSON() ([]byte, error) {
 	return json.Marshal(d.Data())
 }
 
+func (d *Doc) UnmarshalJSON(data []byte) error {
+	return json.Unmarshal(data, &d.data)
+}
+
 // --------------------------------------------------------------------------------
 
 func (d *Doc) path(path ...string) (paths []string) {