Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
A way of configuring the server to listen on a unix socket.
For example you could join the listenaddr and the port into a
single option called listen. Then the listen option could either
get passed localhost:1234 or unix:/tmp/gotify.sock.

Describe alternatives you've considered
n/a

Additional context
n/a