goutil is just a collection of go common used method
Statistics is used to stat realtime data in a web server or a backgroud service
It contain a main type and a sub type, and the third is the key string you want to calculate
eg: Type:API SubType: User Key:get
statis := NewStatistics(10000, 10, "2006-01-02 15:04:05", MockGetTime)
item := Item{Type:"API", SubType:"User", Key:"get"}
statis.AddItem(item)
//Get a data value
data := statis.GetInfoByTypeAndSubType("API", "User")
// data format
// map["time"] = "2017-01-01 12:12:00"
// map["get] = 123
GetDayRange is used to get a range of start and end time, see the comment for usage