to find the last index of the array in mongodb

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.Right now i m getting all the documents of the employee and then find the last index.It is like overloading my RAM as i need to retrieve 1000 of record of employee and store it in ram before finding the last index of the array
My struct is as follows

 type (
        Employee struct {
            Name               string
            Password           string
            EmpId              string 
           EmailAddress       string
           Position           string
           Gender             string
           Nationality        string
           Department         string
           MaritalStatus      string
           Approvedby         string
           JoinDate           time.Time
           ConfirmationDate   time.Time
           EndDate            time.Time
            Leave             []*LeaveInfo  
        }
        LeaveInfo struct {
            Total        float64
            Id           int
            Days         float64
            From        time.Time
             To          time.Time  
            Status       string
            Certificate  []*CertificateInfo
        }
        CertificateInfo struct {
            FileName string
            FileType string
            FileSize int
        }

Here is how i do in my application

 My code is follows
    
    employee := Employee{}
    err = c.Find(bson.M{
                  "empid": "1234"
                 }).One(&result)
    if err != nil {
            log.Fatal(err)
    }
          name:=result.Name        
          lastindex:= result.LeaveInfo[len(result.LeaveInfo)-1].Id

As you can see i retrive the whole employee data and then find the Id of the last document.Is there any better way to do this.Appreciate any help.Please ...Thanks..

> Newly Added Codes

 This code is based on your example
    
   var result bson.M
    
    query := bson.M{"empid": "1234"}  // gets the employee you are interested in
    match := bson.M{"$match": query}  // Set up the match part of the pipeline
    unwind := bson.M{"$unwind": "$leave"}  // sets up the leave field to be unwound
    
    pipeline := []bson.M{match, unwind,{
    "$project":bson.M{
           "ID":bson.M{
                "$slice": []interface{}{"$leave.id", -1},
        }
       }
    
  
    iter := postCollection.Pipe(pipeline).Iter()
    for iter.Next(&result) {
        fmt.Printf("%+v\n", result)
    }
    iter.Close()

This code gives me lot of same document like 542 documents .But all these document are same...

If you are running a version on Mongo which has $slice in it, It was introduced in 2.4, you can use it in a Find with the addition of a Select Function, which works like project.

err = c.Find(bson.M{"empid": "1234"}).Select(bson.M{"name": 1, "leave": bson.M{"$slice": -1}}).One(&result) // result is an Employee struct

Otherwise, aggregation is your friend. You need to use a pipeline and unwind the Employee Leave field.

There are a few simple steps:

1. Define a result record based on your Employee record where the Leave field is defined as a single LeaveInfo rather than a slice of LeaveInfos, eg

   EmployeeResult struct {
   Name string bson:"name"
   Leave LeaveInfo bson:"leave"
   }
   Do not forget to make the bson tag the same name as the LeaveInfo tag in the Employee struct.

2. Then create a pipeline with a couple of stages:

   query := bson.M{"empid": "1234"} // gets the employee you are interested in
   match := bson.M{"$match": query} // Set up the match part of the pipeline
   unwind := bson.M{"$unwind": "$leave"} // sets up the leave field to be unwound
   pipeline := []bson.M{match, unwind} // the pipeline you are passing to pipe. I like to split the parts of the pipe call up for clarity and ease of later modification

3. Call Pipe with the pipeline as a parameter then Iter over the results, this should give you one LeaveInfo at a time

   var (
   result EmployeeResult
   )
   iter := postCollection.Pipe(pipeline).Iter()
   for iter.Next(&result) {
   fmt.Printf("%+v\n", result)
   }
   iter.Close()

4. At the end of the loop, result will have the last item in the list, or be blank if nothing was read.