There is nothing like in-built utilities for that you can use the command like this :
You can create your custom script like this :
for i in `cat app_server.txt` ; do echo $i ; ssh -i /path/to/your_key.pem $i "sudo docker swarm join --token your-token-here ip-address-of-manager:port" ; done
Here app_server.txt is the ip address of your worker node that you want to add in your swarm.
--token : your token generated by manager on docker swarm init