logger

type Config struct {
	Target     string //日志输出目标。一般是console或者file
	LogFile    string //日志输出文件
	MaxSize    int    //日志文件最大尺寸
	MaxBackups int    //最大备份数
	MaxAge     int    //最大停留
	Level      int
}

type Level int8

type Logger interface {
	Log(level Level, v ...interface{})
	// Logf writes a formatted log entry
	Logf(level Level, format string, v ...interface{})

	Debugf(format string, v ...interface{})
	Fatalf(format string, v ...interface{})
	Infof(format string, v ...interface{})

	// String returns the name of logger
	String() string

	Options() Options
}

type Option func(*Options)

type Options struct {
	// It's common to set this to a file, or leave it default which is `os.Stderr`
	Out io.Writer
	// Alternative options
	Context context.Context
	// fields to always be logged
	Fields map[string]interface{}
	// Caller skip frame count for file:line info
	CallerSkipCount int
	// The logging level the logger should log at. default is `InfoLevel`
	Level Level
}