I've been using `math/rand` instead of `crypto/rand` where `crypto/rand` was absolutely needed. This resulted in static keys being used in early versions of dnscrypt-proxy2.

The reason is that I'm using the VSCode extension that automatically adds imports. In all the source files requiring secure randomness, I carefully imported `crypto/rand` manually, but I forgot to do it in one of the files. Everything compiled and worked file, and I didn't notice that in that specific file, the extension silently added a `math/rand` import.

Since then, I import `crypto/rand` as `cryptorand` to avoid the wrong `rand` to be automatically imported.

By the way, Zig also uses a ChaCha8-based random number generator, and for cryptographic operations, people can't supply their own generator; the secure one is always used. For testing, some functions accept an explicit seed. For constrained environments, the standard library also includes a smaller one based on the Ascon permutation and the Reverie construction.