Teamspeak transfers voice data to clients over UDP from port 9987.
Caddy speaks HTTP(S) over TCP, usually on ports 80/443. The two are not compatible, despite being capable of working on the same port.
If your Teamspeak is running on an internal server (i.e. 192.168.1.13) and you need to run a program at the edge of your network to proxy to it, I suggest ts3proxy:
Edit: Actually, you might be able to use the (disclaimed as beta) net server type to essentially port forward via Caddy: