brew install mongo brew services start mongodb
About brew services
Integrates Homebrew formulae with macOS' launchctl manager.
> Services can be added to either /Library/LaunchDaemons or ~/Library/LaunchAgents.
> Basically, items in /Library/LaunchDaemons are started at boot,
> while those in ~/Library/LaunchAgents are started at login.
> When started with sudo, it operates on /Library/LaunchDaemons;
> otherwise, it operates on ~/Library/LaunchAgents.