graphql-ws subscription behaviour is not compatible with AWS api.

[ret-smart]

Screenshot
i set a console.log at validateMessage:

"id": "5c87a716-0053-4755-b949-ef2cdf1d038c",
  "type": "subscribe",
  "payload": {
    "query": "subscription OnUpdateDatapoint {\n        onUpdateDatapoint {\n            id\n            value\n        }\n    }",
    "variables": {},
    "extensions": {
      "authorization": {
        "host": "XXXX.appsync-api.eu-west-1.amazonaws.com",
        "authorization": "Bearer Token"
      }
    }
  }
}
message= {
  "type": "ka"
}
message= {
  "type": "error",
  "payload": {
    "errors": [
      {
        "errorType": "UnsupportedOperation",
        "message": "unknown not supported through the realtime channel"
      }
    ]
  }
}

Error: Error: "error" message expects the 'id' property to be a string, but got undefined

Expected Behaviour
[https://docs.aws.amazon.com/en_us/appsync/latest/devguide/real-time-websocket-client.html]
i checked the websocket environment with this specification and it has worked with wscat.

the ka message leads to an error.

Actual Behaviour
I checked the source code the i saw tht the component uses other requests than AWS does.

Debug Information
create an AWS amplify api and check subscription.

Further Information
I can send my source code, if requested.

[enisdenjo]

Duplicate of #241.