Retry when io.readAll fail

Hi, I recently learned how [golang make http request](https://groups.google.com/g/golang-nuts/c/LPcNdWmwjKE/m/XijW5TWh5wIJ):
1. send request
2. receive header containing io.reader
3. use io.reader to make follow-up request for the actual payload

I ran into a scenario where we failed on step 3 and did not see retry, and I am not really sure how to make it retryable with [go-retryablehttp](https://github.com/hashicorp/go-retryablehttp). Seems like this [Do](https://github.com/hashicorp/go-retryablehttp/blob/main/client.go#L649) function isn't returning the actual payload directly.