Package rehttp implements an HTTP Transport (an http.RoundTripper) that handles retries. See the godoc for details.
Please note that rehttp requires Go1.6+, because it uses the http.Request.Cancel field to check for cancelled requests. It should work on Go1.5, but only if there is no timeout set on the *http.Client. Go's stdlib will return an error on the first request if that's the case, because it requires a RoundTripper that implements the (now deprecated in Go1.6) CancelRequest method.
On Go1.7+, it uses the context returned by http.Request.Context to check for cancelled requests.
$ go get github.com/PuerkitoBio/rehttp
The BSD 3-Clause license.