When talking to an HTTP2 server, there are situations where it needs to
"rewind" the Request.Body. To allow this, we have to set up the Request.GetBody
function to return a brand new instance of the body.
If not set, we can end up with the following error:
http2: Transport: cannot retry err [http2: Transport received Server's graceful shutdown GOAWAY] after Request.Body was written; define Request.GetBody to avoid this error
See this commit for more information: cffdcf672a
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