Had an AWS STS AssumeRole problem today; digging in it turned out the problem was that AssumeRole was not actually being invoked. Digging around I was unsurprised to find that @ben11kehoe had already clearly stated the problem and GitHub user petitout had example Go code with the right way to do it.
https://github.com/aws/aws-sdk-go-v2/issues/1382#issuecomment-1010464182
