logger

type Fields map[string]interface{}

type Logger interface {
	// Debug uses fmt.Sprint to construct and log a message.
	Debug(args ...interface{})

	// Info uses fmt.Sprint to construct and log a message.
	Info(args ...interface{})

	// Warn uses fmt.Sprint to construct and log a message.
	Warn(args ...interface{})

	// Error uses fmt.Sprint to construct and log a message.
	Error(args ...interface{})

	// Panic uses fmt.Sprint to construct and log a message, then panics.
	Panic(args ...interface{})

	// Fatal uses fmt.Sprint to construct and log a message, then calls os.Exit.
	Fatal(args ...interface{})

	// Debugf uses fmt.Sprintf to log a templated message.
	Debugf(template string, args ...interface{})

	// Infof uses fmt.Sprintf to log a templated message.
	Infof(template string, args ...interface{})

	// Warnf uses fmt.Sprintf to log a templated message.
	Warnf(template string, args ...interface{})

	// Errorf uses fmt.Sprintf to log a templated message.
	Errorf(template string, args ...interface{})

	// Panicf uses fmt.Sprintf to log a templated message, then panics.
	Panicf(template string, args ...interface{})

	// Fatalf uses fmt.Sprintf to log a templated message, then calls os.Exit.
	Fatalf(template string, args ...interface{})

	WithFields(keyValues Fields) Logger
}