Allow web server to listen on IPv6

[tansanDOTeth]

I am trying to get this to work in a private network, and it seems Fiber needs to be setup with this configuration for it to work:
https://docs.railway.com/guides/private-networking#go-fiber

fiber is a web framework for Go. When configuring your Fiber app, you should set the Network field to tcp to have it listen on IPv6 as well as IPv4:
app := fiber.New(fiber.Config{
Network: "tcp",
ServerHeader: "Fiber",
AppName: "Test App v1.0.1",
})

I'm not really familiar enough with go to make a PR here, but I believe here and possibly a few other areas could be updated to support this.

smoothmq/cmd/smoothmq/server/server.go

Lines 90 to 92 in a6094b1

	app := fiber.New(fiber.Config{
	DisableStartupMessage: true,
	})