Pure-Go implementation of BLAKE3 cryptographic hash

 blake3 implements the BLAKE3 cryptographic hash function
 (https://github.com/BLAKE3-team/BLAKE3). This implementation aims to
 be performant without sacrificing (too much) readability, in the hopes
 of eventually landing in x/crypto.
 .
 In addition to the pure-Go implementation, this package
 also contains AVX-512 and AVX2 routines (generated by avo
 (https://github.com/mmcloughlin/avo)) that greatly increase performance
 for large inputs and outputs.