Need to include $each and $position with $push in MongoDB and golang(mgo)

[Rajesh Kumar]

1.In the back end i m using go lang and for database i use mongoDB. I m trying to find the last document inserted in the embedded array so i can retrieve the document in the last array index without knowing its index.Is is possible?? After researching on this i came to know that its not possible.So i m thinking of using $push,$each and $position.Here i can set the position to 0 so the newly added document will be in 0 so i can retreive it using the index 0.

  Here is bson format
    {
    empid:"L12"
    AnnualLeave:[
        {
        "atotal" : 20,
        }
    ]
    }



 Here is my schema


 type (
            Employee struct {
                EmpId          string
                AnnualLeave    []*AnnualLeaveInfo
            }
             AnnualLeaveInfo struct {
                ATotal          int64   
            }


        I use the mgo statement as follows`enter code here`

 c.Update(bson.M{"empid": "string"}, bson.M{"$push": bson.M{"annualleave":bson.M{"$each":
         bson.M{"atotal": 4},"$position":0}}

2.Please advice me as well how to decrement the ATotal of the previous document attached and keep it as the value of the atotal of the new document. Please help me.Thanks