log

type Fields map[string]interface{}

type Logger interface {
	Printf(format string, args ...interface{})
	Debugf(format string, args ...interface{})
	Infof(format string, args ...interface{})
	Warnf(format string, args ...interface{})
	Warningf(format string, args ...interface{})
	Errorf(format string, args ...interface{})
	Fatalf(format string, args ...interface{})
	Panicf(format string, args ...interface{})

	Print(args ...interface{})
	Debug(args ...interface{})
	Info(args ...interface{})
	Warn(args ...interface{})
	Warning(args ...interface{})
	Error(args ...interface{})
	Fatal(args ...interface{})
	Panic(args ...interface{})

	WithFields(Fields) Logger

	// Output set output writer
	Output(io.Writer) Logger
}