forgeConn() in examples is broken

[gaukas]

As mentioned in #117, this issue has been there for awhile.

Description

forgeConn() in the example in examples folder is broken and crashing the example due to null pointer being dereferenced.

Cause

The cipher suite checking in tls.MakeConnWithCompleteHandshake() doesn't work with TLS 1.3 yet.

Notes

We could find a TLS 1.2 host to demonstrate the example and/or add TLS 1.3 support for MakeConnWithCompleteHandshake().