golog

type Logger interface {
	// Debug logs to stdout
	Debug(arg interface{})
	// Debugf logs to stdout
	Debugf(message string, args ...interface{})

	// Error logs to stderr
	Error(arg interface{})
	// Errorf logs to stderr
	Errorf(message string, args ...interface{})

	// Fatal logs to stderr and then exits with status 1
	Fatal(arg interface{})
	// Fatalf logs to stderr and then exits with status 1
	Fatalf(message string, args ...interface{})

	// Trace logs to stderr only if TRACE=true
	Trace(arg interface{})
	// Tracef logs to stderr only if TRACE=true
	Tracef(message string, args ...interface{})

	// TraceOut provides access to an io.Writer to which trace information can
	// be streamed. If running with environment variable "TRACE=true", TraceOut
	// will point to os.Stderr, otherwise it will point to a ioutil.Discared.
	// Each line of trace information will be prefixed with this Logger's
	// prefix.
	TraceOut() io.Writer

	// IsTraceEnabled() indicates whether or not tracing is enabled for this
	// logger.
	IsTraceEnabled() bool

	// AsStdLogger returns an standard logger
	AsStdLogger() *log.Logger
}