Hello, you've tagged this question with "AWS Storage Gateway." Unfortunately, this isn't a SGW related question. You will receive better response if you tag this with "S3" or "SDK" related tags.

Thank you for reaching out to AWS re:Post, We are continuing to build this collection of code samples in the article -> https://docs.aws.amazon.com/code-samples/latest/catalog/go-s3-upload_arbitrary_sized_stream.go.html

If a code you are looking for is not there then a request would need to be raised to have it created, hence I request you to raise a support case with AWS Support. We do not currently have a service for providing on-demand code for customer.