improve concurrency

[exaexa]

improve network communication by exploiting local concurrency (following some measurements from JuliaLang/julia#44671 )

[laurentheirendt]

why master ?

[codecov]

Codecov Report

Merging #40 (27fdead) into develop (e1039a1) will decrease coverage by 0.06%.
The diff coverage is 100.00%.

❗ Current head 27fdead differs from pull request most recent head a777468. Consider uploading reports for the commit a777468 to get more accurate results

@@             Coverage Diff             @@
##           develop      #40      +/-   ##
===========================================
- Coverage    87.62%   87.55%   -0.07%     
===========================================
  Files            4        4              
  Lines          194      209      +15     
===========================================
+ Hits           170      183      +13     
- Misses          24       26       +2     

Impacted Files	Coverage Δ
src/base.jl	95.55% <100.00%> (+0.55%)	⬆️
src/io.jl	100.00% <100.00%> (ø)
src/tools.jl	77.77% <100.00%> (-0.72%)	⬇️

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[exaexa]

fixed to develop