Transport.Proxy is documented as only supporting the http and socks5
schemes. If one tries to use it for https URLs, they end up with a
cryptic error like:
http: TLS handshake error from [...]: tls: oversized record received with length 20037
This is because Transport simply skips TLS if Proxy is non-nil, since it
knows it doesn't support Proxy with https.
However, that error is very confusing and it can take a while to figure
out what's going on. Instead, error if Proxy is used and it returns an
unsupported scheme.
Updates #19493.
Change-Id: Ia036357011752f45bb9b8282a4ab5e31bc8d1a69
Reviewed-on: https://go-review.googlesource.com/66010
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Tom Bergan <tombergan@google.com>