Because tls.Config now requires more fields to be set in order for tls-alpn to work, Manager provides a new TLSConfig method for easier setup. This CL also adds a new internal package for end-to-end tests. The package implements a simple ACME CA server. Fixes golang/go#25013 Fixes golang/go#25901 Updates golang/go#17251 Change-Id: I2687ea8d5c445ddafad5ea2cdd36cd4e7d10bc86 Reviewed-on: https://go-review.googlesource.com/125495 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>