Get multiple cached values

[raeidish]

Closes #324

It works but it's not always faster, the sweet spot where the multi is faster seems to be using 512 shards. I tried using batches and getting all keys at once.

[raeidish]

if you find anyway to improve it please let me know! i tried a few things but can't seem to get it faster.
@cristaloleg, @janisz

[raeidish]

I forgot to add the locked shard to the map fixing it made a big difference

[cristaloleg]

Please reformat with gofmt

[codecov-commenter]

Codecov Report

Merging #379 (e894b71) into main (58fe2d2) will increase coverage by 0.85%.
The diff coverage is 100.00%.

❗ Current head e894b71 differs from pull request most recent head c366663. Consider uploading reports for the commit c366663 to get more accurate results

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@@            Coverage Diff             @@
##             main     #379      +/-   ##
==========================================
+ Coverage   88.66%   89.52%   +0.85%     
==========================================
  Files          15       15              
  Lines         794      821      +27     
==========================================
+ Hits          704      735      +31     
+ Misses         76       73       -3     
+ Partials       14       13       -1     

Files	Coverage Δ
bigcache.go	94.07% <100.00%> (+1.11%)	⬆️
shard.go	92.10% <100.00%> (+1.61%)	⬆️

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[raeidish]

Got a bit of a locking issue, when stats is enabled the shard tries to wlock but as it is now it’s already rlocked. This causes a deadlock issue, I’m thinking about moving the hit call outside getWithoutLock.

[raeidish]

seems like my test was failing because it was too big for the github action 🙂 looks ok now though.

[raeidish]

This is ready for another review 🙂 @janisz