Merge pull request #20 from pedrohb88/prevent-race

prevent race between Balancer check and Close

cleanup balancer connection and healthcheck (#19)

* cleanup balancer connection and healthcheck

* remove concurrence package

* close replicationConnection

* Add Server.Close

fix open connections order

fix open connections order

refactor(health): replace mutex with atomic

fix(race): include mutex to avoid race conditions in health (#13)

feat(health): inlcude IO status (#12)

server up when is connected but has replication errors

Avoid concurrently status check + Go modules (#9)

* Migrate to go modules

* initial check async + prevent multiple checks on database