v1.0.12: Fix Race (#13)

* reverse iterator init

* some fixes

* fix reverse iterator seaklowerbound

* fix tests

* fix track channels

* longest prefix on txn

* some fixes

* revisit

* todo revisit

* major code refactor

* some minor fixes

* add lru

* fix bugs

* added walk func

* add more tests

* some prog

* some progress track mutate

* some progress

* fix tests

* some optimizations

* some memory optimizations

* fix tests

* minor fixes

* some minor fixes

* some fixes

* fix delete prefix

* some fixes

* init stack

* fix seek lower bound

* clone

* fix watch

* fix clone bug

* some fixes for go mem db

* merge absl

* Fix race

* fix go mod

* fix race in add child

* fix last memdb test

* clone

* fix memdb last tests

* fix race