logger

type Logger interface {
	// Printf will be used for informational messages. These can be thought of
	// having an 'Info'-level in a structured logger.
	Printf(string, ...interface{})
	// Panicf will be only called an unexpected programming error such as a type
	// assertion which should never fail. Regular errors will be returned out
	// from the library.
	Panicf(string, ...interface{})
}