logger

type Config struct {
	Dir          string
	ID           string
	Name         string
	Version      string
	Debug        bool
	MaxAge       time.Duration
	RotationTime time.Duration
	RotationSize int64  // 单位字节
	Level        string // debug/info/warn/error

	Sampler Sampler // 采样器
}

type Sampler struct {
	TickSec    int `command:"时间窗口(秒)"`
	First      int `command:"每个时间窗口内记录的前N条日志"`
	Thereafter int `command:"超过N条后每M条记录一次"`
}