Revise version negotiation on the Go half.

This is in preparation for supporting multiple TLS 1.3 variants.

Change-Id: Ia2caf984f576f1b9e5915bdaf6ff952c8be10417
Reviewed-on: https://boringssl-review.googlesource.com/17526
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
diff --git a/ssl/test/runner/conn.go b/ssl/test/runner/conn.go
index fce0049..61fc9d3 100644
--- a/ssl/test/runner/conn.go
+++ b/ssl/test/runner/conn.go
@@ -35,6 +35,7 @@
 	// constant after handshake; protected by handshakeMutex
 	handshakeMutex       sync.Mutex // handshakeMutex < in.Mutex, out.Mutex, errMutex
 	handshakeErr         error      // error resulting from handshake
+	wireVersion          uint16     // TLS wire version
 	vers                 uint16     // TLS version
 	haveVers             bool       // version has been negotiated
 	config               *Config    // configuration passed to constructor