fix: listen error under ipv6 host

[dnomd343]

error recurrence

~/kcptun # ss-libev-server -s ::1 -p 12345 -k dnomd343 -m aes-256-ctr --plugin ./kcptun-server
 2022-03-04 16:50:19 INFO: plugin "./kcptun-server" enabled
 2022-03-04 16:50:19 INFO: initializing ciphers... aes-256-ctr
 2022-03-04 16:50:19 INFO: Stream ciphers are insecure, therefore deprecated, and should be almost always avoided.
 2022-03-04 16:50:19 INFO: tcp server listening at [::1]:60531
 2022-03-04 16:50:19 INFO: running from root user
2022/03/04 16:50:20 main.go:398: version: SELFBUILD
2022/03/04 16:50:20 main.go:111: address ::1:12345: too many colons in address
github.com/xtaci/kcp-go.ListenWithOptions
        /root/go/pkg/mod/github.com/xtaci/[email protected]+incompatible/sess.go:970
main.main.func1
        /root/kcptun/server/main.go:430
github.com/urfave/cli.HandleAction
        /root/go/pkg/mod/github.com/urfave/[email protected]/app.go:524
github.com/urfave/cli.(*App).Run
        /root/go/pkg/mod/github.com/urfave/[email protected]/app.go:286
main.main
        /root/kcptun/server/main.go:484
runtime.main
        /usr/lib/go/src/runtime/proc.go:255
runtime.goexit
        /usr/lib/go/src/runtime/asm_amd64.s:1581
 2022-03-04 16:50:20 ERROR: plugin service exit unexpectedly
 2022-03-04 16:50:20 INFO: error on terminating the plugin.