logger

type Logger interface {
	// Trace logs a Trace event.
	//
	// Even more fine-grained information than Debug events.
	// Loggers not supporting this level should fall back to Debug.
	Trace(msg string, keyvals ...interface{})

	// Debug logs a Debug event.
	//
	// A verbose series of information events.
	// They are useful when debugging the system.
	Debug(msg string, keyvals ...interface{})

	// Info logs an Info event.
	//
	// General information about what's happening inside the system.
	Info(msg string, keyvals ...interface{})

	// Warn logs a Warn(ing) event.
	//
	// Non-critical events that should be looked at.
	Warn(msg string, keyvals ...interface{})

	// Error logs an Error event.
	//
	// Critical events that require immediate attention.
	// Loggers commonly provide Fatal and Panic levels above Error level,
	// but exiting and panicing is out of scope for a logging library.
	Error(msg string, keyvals ...interface{})
}