possible to make this into an lru cache with fixed size? so that it can automatically remove items based on fifo

[hiqsociety]

1. possible to make this into an lru cache with fixed size? so that it can automatically remove items based on fifo

2. how does this compare with art?
   https://github.com/plar/go-adaptive-radix-tree
   any benchmarks on speed and mem storage size used?