Not passing context.Context to http.Request context

[snabb]

The package is not currently accepting context.Context parameter from the Lambda runtime. Therefore the downstream http.Request is lacking it also.

As a result the http handler can not observe the Deadline and is unable to cancel the request gracefully.

See:
https://docs.aws.amazon.com/lambda/latest/dg/go-programming-model-context.html
https://godoc.org/context