```go
import (
    "github.com/dalu/mongostore"
)

    func main() {
	    ctx := context.Background()
	    client, err := mongo.Connect(ctx, options.Client().ApplyURI("mongodb://localhost:27017"))
	    err = client.Ping(ctx, readpref.Primary())
	    if err != nil {
    		panic(err)
    	}

	    store := mongostore.NewMongoStore(client, "test", "sessions", 3*time.Second, []byte("hellol-worlol"))
	    store.Options.Path = "/"
	    store.Options.MaxAge = 86400 * 30 * 365
	    defer store.Close()

        // Get a session.
        session, err := store.Get(req, "session-key")
        if err != nil {
            log.Println(err.Error())
        }

        // Add a value.
        session.Values["foo"] = "bar"

        // Save.
        if err = sessions.Save(req, rw); err != nil {
            log.Printf("Error saving session: %v", err)
        }
    }
```