@Wei had been looking into replacing zond/gotomic. That package is also not optimized for performance, and is considering more expensive both in terms of RAM and CPU.
This is also one of the projects that needs work – to implement a lock-free hash map, which can support, Get, Put and Iterate. The challenge here is growth. zotomic is based on an interesting paper which uses Linked List for growth. From what I understand, there is a newer paper which claims to be faster. So, definitely worth researching and implementing.