In golang, array is auto-expanding so the children array allocates more space than its length, which depends on the golang internal implementation.

> "Child nodes are stored in an array orderly, and checked by binary-search but not indexed by remainders, array indexing will result redundancy entries, this is for less memory usage, with a bit performance loss. "

I just cannot find some way (such as linked list?) to use the exact space with at-least binary-search time complexity.