Do not run letsencrypt watcher unless explicitly enabled (#876)
Do not run letsencrypt watcher unless explicitly enabled (#876)

LetsEncrypt is a third party service, and it is a bad idea to depend on it unless the user really wants.

While it is run in separate goroutine, it still can cause memory leaks, panics, and etc.
mvdan/tyk,lonelycode/tyk,mvdan/tyk,lonelycode/tyk,mvdan/tyk,mvdan/tyk,mvdan/tyk,lonelycode/tyk,mvdan/tyk,mvdan/tyk,mvdan/tyk