Document error behavior for SQS based events

[tnine]

The existing examples for SQS message lamba invocations are very simple.

https://github.com/aws/aws-lambda-go/blob/master/events/README_SQS.md

It would be useful to add 2 additional examples.

Failing all messages for retry

Assuming multiple SQS messages are received, is it possible to return an error such that they are retried? I assume this is the default behavior, but it is not called out clearly in the examples.

Failing single messages/Acking individual messages

Assume 3 messages are received. The first message succeeds, the second fails, and the third succeeds. Can the lambda client use the SQS SDK in conjunction with the SQSMessage.Handle to delete messages 1, and 3 directly, causing only message 2 to be retried?

The above use cases are valid use cases in SQS queue consumption, but the documentation in lambda invocation is not clear on how to accomplish these use cases. If they could be added, it would be very helpful for new users.

[gogingersnap777]

@bmoffatt I am looking around this repo for issues I can possible contribute to. Is this issue still something that can be picked up?