support darwin

[gedw99]

sudo ./immugw service install --config ./configs/immugw.toml
Password:
To provide the maximum level of security, we recommend running immugw on a different machine than immudb server. Continue ? [Y/n]Y
Error: exec: "groupadd": executable file not found in $PATH
Usage:
  immugw service [install uninstall start stop restart status] [flags]

Examples:
Install the immutable database
sudo ./immugw service install    -  Installs the daemon
sudo ./immugw service stop       -  Stops the daemon
sudo ./immugw service start      -  Starts initialized daemon
sudo ./immugw service restart    -  Restarts daemon
sudo ./immugw service uninstall  -  Removes daemon and its setup
Uninstall immugw after 20 second
sudo ./immugw service install --time 20 immugw

Flags:
  -h, --help       help for service
  -t, --time int   number of seconds to wait before stopping | restarting the service

Global Flags:
      --config string   config file (default path are configs or $HOME. Default filename is immugw.toml)

exec: "groupadd": executable file not found in $PATH

Looks like the dependency your using supports darwin: https://github.com/codenotary/daemon/blob/master/daemon_darwin.go

Maybe its useful but these as you know also work for desktops and servers

github.com/kardianos/osext v0.0.0-20190222173326-2bc1f35cddc0
github.com/kardianos/service v1.2.0