Add pool of hashes for HMAC

[storozhukBM]

This is an experimental branch where we try to improve the performance of hsAlg hashers.

Current results:

name                 old time/op    new time/op    delta
HS/Sign-HS256-4        3.02µs ± 1%    2.80µs ± 5%   -7.30%  (p=0.000 n=10+10)
HS/Verify-HS256-4      1.53µs ± 2%    1.18µs ± 1%  -22.91%  (p=0.000 n=10+9)
HS/Sign-HS384-4        3.44µs ± 4%    2.81µs ± 4%  -18.39%  (p=0.000 n=10+9)
HS/Verify-HS384-4      1.81µs ± 1%    1.29µs ± 2%  -28.81%  (p=0.000 n=9+9)
HS/Sign-HS512-4        3.39µs ± 1%    2.87µs ± 4%  -15.24%  (p=0.000 n=9+10)
HS/Verify-HS512-4      1.86µs ± 5%    1.30µs ± 1%  -29.97%  (p=0.000 n=9+9)

name                 old alloc/op   new alloc/op   delta
HS/Sign-HS256-4        1.33kB ± 0%    0.85kB ± 0%  -36.14%  (p=0.000 n=10+10)
HS/Verify-HS256-4        512B ± 0%       32B ± 0%  -93.75%  (p=0.000 n=10+10)
HS/Sign-HS384-4        1.70kB ± 0%    0.90kB ± 0%  -47.17%  (p=0.000 n=10+10)
HS/Verify-HS384-4        848B ± 0%       48B ± 0%  -94.34%  (p=0.000 n=10+10)
HS/Sign-HS512-4        1.78kB ± 0%    0.98kB ± 0%  -45.05%  (p=0.000 n=10+10)
HS/Verify-HS512-4        864B ± 0%       64B ± 0%  -92.59%  (p=0.000 n=10+10)

name                 old allocs/op  new allocs/op  delta
HS/Sign-HS256-4          18.0 ± 0%      13.0 ± 0%  -27.78%  (p=0.000 n=10+10)
HS/Verify-HS256-4        6.00 ± 0%      1.00 ± 0%  -83.33%  (p=0.000 n=10+10)
HS/Sign-HS384-4          18.0 ± 0%      13.0 ± 0%  -27.78%  (p=0.000 n=10+10)
HS/Verify-HS384-4        6.00 ± 0%      1.00 ± 0%  -83.33%  (p=0.000 n=10+10)
HS/Sign-HS512-4          18.0 ± 0%      13.0 ± 0%  -27.78%  (p=0.000 n=10+10)
HS/Verify-HS512-4        6.00 ± 0%      1.00 ± 0%  -83.33%  (p=0.000 n=10+10)

[codecov]

Codecov Report

Merging #44 into master will increase coverage by 0.24%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #44      +/-   ##
==========================================
+ Coverage   85.58%   85.83%   +0.24%     
==========================================
  Files          12       12              
  Lines         458      466       +8     
==========================================
+ Hits          392      400       +8     
  Misses         39       39              
  Partials       27       27              

Impacted Files	Coverage Δ
algo_hs.go	82.45% <100.00%> (+2.86%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1d58f52...0867de5. Read the comment docs.

[cristaloleg]

🎉