TLSv1.3 is currently in its early stages. But, as of 21 March 2018, TLS 1.3 is an Internet Draft proposed to Internet Standard. It is based on the earlier TLS 1.2 specification.
TLSv1.3 brings with it a lot of improvements in the aspects of speed and security. This has led to a re-design of the way the protocol performs handshake. Filippo Valsorda had a great talk describing the major benefits of TLS 1.3 vs that of TLS 1.2. We recommend that you spend some time in understanding the differences in the way TLSv1.2 and TLSv1.3 work.