Migrate to go1.15 and confluent-kafka-go v1.5.2 (#10) (#17)

* update confluent-kafka-go dependency to v1.5.2

* fix build

* fix tests

* add logs

* Fix worflow

* Fix integration test (#9)

* use environnement variable to define boostrap server

Co-authored-by: Laurent Dechoux <34473609+iotafr@users.noreply.github.com>
Co-authored-by: Vincent Composieux <vincent@composieux.fr>