The api key you get after register on https://developer.clashofclans.com if you don't know your public ip go to https://www.whatismyip.com/
Usage of ./clashclient:
-apikey string
API key to use, can also be set in env var COC_KEY (default "")
-clan string
Clan tag to view, can also be set in env var COC_CLANTAG (default "")
-port string
Port to run service on, can also be set in env var COC_PORT (default "8888")