json: cannot unmarshal string into Go struct field APIGatewayProxyRequestContext.authorizer

[Yenchu]

When integrating with api gateway WebSocket API, got error in CloudWatch log:
json: cannot unmarshal string into Go struct field APIGatewayProxyRequestContext.authorizer of type map[string]interface {}: UnmarshalTypeError null

To log requestContext info, the field authorizer is empty:
requestContext:map[stage:... authorizer: messageId:<nil>...

[piotrkubisa]

The type definition is a bit different for a Websocket events - for an instance (I might don't recall correctly) there are at least two fields which are missing in the requestContext:

connectionId: string
connectedAt: number

https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-websocket-api-logging.html

That said, aws-lambda-go repository lacks of struct for an API Gateway usage with a websocket. It would be great if someone could copy and paste the raw event payload here or make an PR and add it into the test data directory and create new struct with a corresponding json tags definition.

[Dasio]

Here is raw event payload

{
    "headers": {
        "Host": "*.execute-api.eu-central-1.amazonaws.com",
        "Sec-WebSocket-Extensions": "permessage-deflate; client_max_window_bits",
        "Sec-WebSocket-Key": "*",
        "Sec-WebSocket-Version": "13",
        "X-Amzn-Trace-Id": "*",
        "X-Forwarded-For": "*.*.*.*",
        "X-Forwarded-Port": "443",
        "X-Forwarded-Proto": "https"
    },
    "isBase64Encoded": false,
    "multiValueHeaders": {
        "Host": [
            "*.execute-api.eu-central-1.amazonaws.com"
        ],
        "Sec-WebSocket-Extensions": [
            "permessage-deflate; client_max_window_bits"
        ],
        "Sec-WebSocket-Key": [
            "*"
        ],
        "Sec-WebSocket-Version": [
            "13"
        ],
        "X-Amzn-Trace-Id": [
            "Root=*"
        ],
        "X-Forwarded-For": [
            "*.*.*.*"
        ],
        "X-Forwarded-Port": [
            "443"
        ],
        "X-Forwarded-Proto": [
            "https"
        ]
    },
    "requestContext": {
        "apiId": "*",
        "authorizer": "",
        "connectedAt": "*",
        "connectionId": "*",
        "domainName": "*.execute-api.eu-central-1.amazonaws.com",
        "error": "",
        "eventType": "CONNECT",
        "extendedRequestId": "*",
        "identity": {
            "accessKey": null,
            "accountId": null,
            "caller": null,
            "cognitoAuthenticationProvider": null,
            "cognitoAuthenticationType": null,
            "cognitoIdentityId": null,
            "cognitoIdentityPoolId": null,
            "sourceIp": "*.*.*.*",
            "user": null,
            "userAgent": null,
            "userArn": null
        },
        "integrationLatency": "",
        "messageDirection": "IN",
        "messageId": null,
        "requestId": "*",
        "requestTime": "07/Jan/2019:09:20:57 +0000",
        "requestTimeEpoch": 1546852857724,
        "routeKey": "$connect",
        "stage": "test",
        "status": ""
    }
}

[Dasio]

These are extra fields in APIGatewayProxyRequestContext

	ConnectedAt        int64       `json:"connectedAt"`
	ConnectionID       string      `json:"connectionId"`
	DomainName         string      `json:"domainName"`
	Error              string      `json:"error"`
	EventType          string      `json:"eventType"`
	ExtendedRequestId  string      `json:"extendedRequestId"`
	IntegrationLatency string      `json:"integrationLatency"`
	MessageDirection   string      `json:"messageDirection"`
	// IDK type of this
	MessageID          interface{} `json:"messageId"`
	RequestTime        string      `json:"requestTime"`
	RequestTimeEpoch   int64       `json:"requestTime"`
	RouteKey           string      `json:"routeKey"`
	Status             string      `json:"status"`

But in WS event it is

	Authorizer   string                      `json:"authorizer"`

Now it's

	Authorizer   map[string]interface{}    `json:"authorizer"`

[jozanza]

Just chiming in here -- I forked and deployed to aws with the code from #159, and it seems that if you do not set an authorizer on your WebSocket route in API Gateway, the marshalling of APIGatewayWebsocketProxyRequest will still fail since it's not able to convert null to map[string]interface{}. Entirely removing the Authorizer field from the struct worked, but that's probably not the best option 😅 .

[bmoffatt]

Authorizer is going to have to be an interface{} to be compatible with all the different ways it can be populated