ng {
            return nil
        }

        fmt.Println("Adding user", event.UserID, "to the promotions list")

        return nil
    },
)`
                }],
            },
            {
                number: 4,
                title: "Introducing a consumer group",
                description: `
                <p>Introducing a consumer group makes messages delivered in a round-robin fashion.</p>
                <p>Each message is processed only once. It is delivered to the group, and the Pub/Sub d