GoLang MongoDB connections leak

Hello

Here is a code example that performs retrieval from MongoDB each second.
My problem is that on each retrieval additional connection is opened (according to MongoDB logs)

Code:
<!-- language: lang-go -->

package main
import (
"os"
"fmt"
"gopkg.in/mgo.v2"
"time"
"gopkg.in/mgo.v2/bson"
)
const (
host1     	= "localhost"
port1    	= "27017"
dbName    	= "test_db"
collectionName  = "TEST_COLLECTION"
)
type Data struct {
InternalId   bson.ObjectId `bson:"_id" json:"_id,omitempty"`
Key1         string
Key2         string
Key3         int64
}
func main() {
fmt.Println("Starting mongo worker ... ")
finished := make(chan bool)
go DoWorkerJob(finished)
<-finished
}
func DoWorkerJob(finished chan bool) {
session, err := GetSession()
defer 	session.Close()
if err != nil {
panic(err)
os.Exit(1)
}
for {
fmt.Println("Retrieving data ...")
collection := GetCollection(*session,collectionName)
allData, err := GetAllRows(collection)
if err != nil {
panic(err)
continue
}
if allData != nil {
fmt.Println("Total retrieved: ", len(allData), " documents.")
}
time.Sleep(time.Duration(1000) * time.Millisecond)
}
finished <- true
}
func GetAllRows(collection *mgo.Collection) ([]Data, error) {
var results []Data
err := collection.Find(nil).All(&results)
if err != nil {
panic(err)
return nil, err
}
return results, nil
}
func GetSession() (*mgo.Session, error) {
fmt.Println("Creating session ...")
MongoDBHosts1 := host1 + ":" + port1
mongoDBDialInfo := &mgo.DialInfo{
Addrs:    []string{MongoDBHosts1},
Timeout:  5 * time.Second,
Database: dbName,
}
mongoSession, err := mgo.DialWithInfo(mongoDBDialInfo)
if err != nil {
panic(err)
return nil, err
}
mongoSession.SetSocketTimeout(5 * time.Second)
mongoSession.SetMode(mgo.Monotonic, true)
session := mongoSession.New()
fmt.Println("Session created!")
return session, nil
}
func GetCollection(session mgo.Session, queueName string) (*mgo.Collection) 
{
fmt.Println("Creating collection ...")
collection := session.Copy().DB(dbName).C(queueName)
fmt.Println("Collection created!")
return collection
}

Program output:

Starting mongo worker ... 
Creating session ...
Session created!
Retrieving data ...
Creating collection ...
Collection created!
Total retrieved:  3  documents.
Retrieving data ...
Creating collection ...
Collection created!
Total retrieved:  3  documents.
Retrieving data ...
Creating collection ...
Collection created!
Total retrieved:  3  documents.
Retrieving data ...

MongoDB logs:

2017-08-03T11:24:53.600+0300 I NETWORK  [initandlisten] waiting for connections on port 27017
2017-08-03T11:25:38.785+0300 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:54591 #1 (1 connection now open)
2017-08-03T11:25:41.952+0300 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:54592 #2 (2 connections now open)
2017-08-03T11:25:45.260+0300 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:54593 #3 (3 connections now open)
2017-08-03T11:26:19.327+0300 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:54594 #4 (4 connections now open)
2017-08-03T11:26:38.797+0300 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:54595 #5 (5 connections now open)
2017-08-03T11:26:41.964+0300 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:54596 #6 (6 connections now open)
2017-08-03T11:26:45.269+0300 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:54597 #7 (7 connections now open)
2017-08-03T11:27:19.338+0300 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:54599 #8 (8 connections now open)
2017-08-03T11:38:37.106+0300 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:54836 #9 (9 connections now open)

What am I doing here wrong ? Number of connections in Mongo gets to thousands what eventually kills it...

each time you copy a session, you should close it.

rewrite your GetCollection and GetAllRows, use one function like:

func FetchData(session mgo.Session, queueName string) ([]Data, error) {
fmt.Println("Creating collection ...")
sess := session.Copy()
collection := sess.DB(dbName).C(queueName)
fmt.Println("Collection created!")
defer  sess.Close() 
var results []Data
err := collection.Find(nil).All(&results)
if err != nil {
panic(err)
return nil, err
}
return results, nil
}

note the line

 defer  sess.Close()