"data" property should be used, not "message"

[andrey-skl]

If server sent event contains "data" property, it is ignored, but "message" used instead: https://github.com/JonnyBGod/react-native-eventsource/blob/master/src/EventSource.js#L58

var event = new EventSourceEvent(ev.type, {
          data: ev.message
        });

[andrey-skl]

Looks like it is fixed in @USFT fork https://github.com/USFT/react-native-eventsource/commit/b716648472ee9782f01a67e3e298f9a630149a29