feat(reader): allow consuming from multiple topics with a group

[dominicbarnes]

This change allows the Reader to consume from multiple topics when being used with a consumer group. To opt into this behavior, you supply config.GroupTopics instead of config.Topic, the default behavior and config is unchanged.

The following open issues would be resolved by this change:

• Reader: consume from multiple topics #595
• Can a consumer consume multiple topics? #564

I've added test cases for several permutations of this new config:

• Topic
• GroupTopics (one value)
• GroupTopics (multiple values)

[achille-roussel]

This change looks great 👍

We've decided to hold on merging until we have had the opportunity to run a production-scale test internally to build confidence that we are not introducing any regressions.

[iAziz786]

@dominicbarnes Thanks for your great work!

We have started to use kafka-go in our products and we are in the process of shipping them to production and we need to consume from multiple topics by one group. As I can see that this is all set to be release is there anything I can do from my end to close this faster?

If closing is not possible at this point can you please guild me with alternatives?

[achille-roussel]

@iAziz786 this change should be ready to go. We wanted to do a bit more production testing before we merge it to master to ensure we aren't introducing any regressions, but nothing else is blocking it.

[iAziz786]

That's good news, although we have moved to confluent go library for now but will move back to kafka-go as soon as this PR is merged.

[xiaokgs]

We have same request to consume from multiple topics, can I ask when this will be merged?
@achille-roussel can you help on this question please?.

[dominicbarnes]

We'll proceed with merging this, we would definitely appreciate some feedback after some testing @iAziz786 !

[achille-roussel]

@iAziz786 @xiaokgs this has been released as part of the v0.4.12 update 👍