log

type InfoLogger interface {
	// Info is used to write a user facing status message.
	//
	// See: Logger.V
	Info(message string)
	// Infof is used to write a Printf style user facing status message.
	Infof(format string, args ...interface{})
	// Enabled should return true if this verbosity level is enabled.
	// on the Logger
	//
	// See: Logger.V
	Enabled() bool
}

type Level int32

type Logger interface {
	// Warn should be used to write user facing warnings.
	Warn(message string)
	// Warnf should be used to write Printf style user facing warnings.
	Warnf(format string, args ...interface{})
	// Error may be used to write an error message when it occurs.
	// Prefer returning an error instead in most cases.
	Error(message string)
	// Errorf may be used to write a Printf style error message when it occurs.
	// Prefer returning an error instead in most cases.
	Errorf(format string, args ...interface{})
	// V() returns an InfoLogger for a given verbosity Level.
	//
	// Normal verbosity levels:
	// V(0): normal user facing messages go to V(0)
	// V(1): debug messages start when V(N > 0), these should be high level
	// V(2): more detailed log messages
	// V(3+): trace level logging, in increasing "noisiness" ... allowing
	// arbitrarily detailed logging at extremely low cost unless the
	// logger has actually been configured to display these (E.G. via the -v
	// command line flag)
	//
	// It is expected that the returned InfoLogger will be extremely cheap
	// to interact with for a Level greater than the enabled level.
	V(level Level) InfoLogger
}