the rust argon2 implementation is ~76 times slower than the golang implementation

[zlianon]

Rust (cargo run: ~2m33s)

use argon2::Algorithm;
use argon2::Argon2;
use argon2::ParamsBuilder;
use argon2::Version;
use rand::thread_rng;
use rand::RngCore;

fn main() {
    let mut salt = [0u8; 16];
    thread_rng().fill_bytes(&mut salt);
    let mut key = [0u8; 32];
    Argon2::new(
        Algorithm::Argon2id,
        Version::V0x13,
        ParamsBuilder::new()
            .m_cost(1048576)
            .t_cost(12)
            .p_cost(8)
            .build()
            .unwrap_or_else(|error| panic!("{}", error)),
    )
    .hash_password_into(b"password", &salt, &mut key)
    .unwrap_or_else(|error| panic!("{}", error));
}

Go (go run: ~2s)

package main

import (
	"crypto/rand"
	"golang.org/x/crypto/argon2"
)

func main() {
	salt := make([]byte, 16)
	rand.Read(salt)
	argon2.IDKey([]byte("password"), salt, 12, 1048576, 8, 32)
}

[tarcieri]

See #104