just wondering how to reach my device behind the router ?

this software wil tell me the WAN IP, but if i want to reach my server using ssh or http, and i cant setup port forwarding on thr router ( because i cant ) then what ?

I have read about tunnels. Its like there are 3 devices in the mix.
my pc (in an NAT environment)
a server in a datacenter with a public static ip
the device (in a NAT environment).

do you know of any golang software that can help me to be able to connect ?