go-radix provides the `radix` package that implements a radix tree.
The package only provides a single `Tree` implementation, optimized
for sparse nodes.

As a radix tree, it provides the following:
 * O(k) operations. In many cases, this can be faster than a hash table since
   the hash function is an O(k) operation, and hash tables have very poor
   cache locality.
 * Minimum / Maximum value lookups
 * Ordered iteration

For an immutable variant, see go-immutable-radix.