v1.9.0

v1.9.0 is a feature release:

• OAUTHBEARER OIDC support
• KIP-140 Admin API ACL support
• Added MockCluster for functional testing of applications without the need
  for a real Kafka cluster (by @SourceFellows and @kkoehler, #729).
  See examples/mock_cluster.

Fixes

• Fix Rebalance events behavior for static membership (@jliunyu, #757, #798).
• Fix consumer close taking 10 seconds when there's no rebalance needed (@jliunyu, #757).

confluent-kafka-go is based on librdkafka v1.9.0, see the
librdkafka release notes
for a complete list of changes, enhancements, fixes and upgrade considerations.