gistfile1.go

package main

import (
  "fmt"
	"os"
)

import (
	"labix.org/v2/mgo"
	"labix.org/v2/mgo/bson"
)

func main() {
	session, err := mgo.Dial("localhost")
	if err != nil {
		panic(err)
	}

	col := session.DB("qbox_test").C("counters")
	col.RemoveId("user_userid")
	err = col.Insert(bson.M{
		"_id": "user_userid",
		"n":   int64(0),
	})
	if err != nil {
		panic(err)
	}
	change := mgo.Change{
		Update:    bson.M{"$inc": bson.M{"n": 1}},
		ReturnNew: true,
	}
	res := map[string]interface{}{}

	_, err = col.FindId("user_userid").Apply(change, &res)
	if err != nil {
		fmt.Printf("%#v\n", err)
		os.Exit(1)
	}
}