Golang: Read full request body but reset it so downstream handlers can still use it.

read-n-reset-request-body.go

func(w http.ResponseWriter, r *http.Request) {

	body, err := io.ReadAll(r.Body)
	if err != nil {

		// do some error handling
		return
	}
	r.Body.Close()

	// since the body has been drained, reconstruct it as a ReadCloser
	// for further consumption downstream
	r.Body = io.NopCloser(bytes.NewBuffer(body))

	next.ServeHTTP(w, r)
}