ListenAndServeTLS and letsencrypt

Hi,
is there a way for you to provide a working sample on how to user manners with letsencrypt ? 
I actually use this command : 
log.Fatal(manners.ListenAndServe(ApiIP, Router))

I would love to use an autoupdate process by crontab like with nginx or apache ...

Thanks for your help !
Stéphane