Official mongo-go-driver using sessions

Question

Is there any example of using sessions with official mongodb driver for golang? I am trying to use sessions to take advantage from transactions and it seems that just reading tests on github I can't find the way to do it.

To be more specific I am struggling now with this:

session, err := pool.StartSession()                                              
   if err != nil {                                                                  
     log.Println("Could not create db session", err)                                
     return events.APIGatewayProxyResponse{                                         
       Body:       err.Error(),                                                     
       StatusCode: http.StatusInternalServerError,                                  
     }, err                                                                         
   }                                                                                
   ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)          
   defer cancel()                                                                   
   defer session.EndSession(ctx)                                                    

    var db *mongo.Database                                                           

Everything fine with code above but when I do:

db = session.Database("testrest")

It gives the error:

session.Database undefined (type mongo.Session has no field or method Database)

Which seems to work with mgo package… How do I select the database and run queries with session?

Answer 1

The solution can be found here: https://github.com/simagix/mongo-go-examples/blob/master/examples/transaction_test.go#L68

if session, err = client.StartSession(); err != nil {
    t.Fatal(err)
}
if err = session.StartTransaction(); err != nil {
    t.Fatal(err)
}
if err = mongo.WithSession(ctx, session, func(sc mongo.SessionContext) error {
    if result, err = collection.UpdateOne(sc, bson.M{"_id": id}, update); err != nil {
        t.Fatal(err)
    }
    if result.MatchedCount != 1 || result.ModifiedCount != 1 {
        t.Fatal("replace failed, expected 1 but got", result.MatchedCount)
    }

    if err = session.AbortTransaction(sc); err != nil {
        t.Fatal(err)
    }
    return nil
}); err != nil {
    t.Fatal(err)
}
session.EndSession(ctx)