debug disables the automatic recovery upon a crash so that you’ll get a nice stack trace.
Normally CoreDNS will recover from panics, using debug inhibits this. The main use of debug is
to help testing. A side effect of using debug is that log.Debug and log.Debugf will be printed
to standard output.
Note that the errors plugin (if loaded) will also set a recover negating this setting.
Disable the ability to recover from crashes and show debug logging: