Diff sync interval & reduce allocate & metrics

[ucwong]

No description provided.

[codecov]

Codecov Report

Merging #46 into master will increase coverage by 0.09%.
The diff coverage is 19.04%.

@@            Coverage Diff             @@
##           master      #46      +/-   ##
==========================================
+ Coverage   24.62%   24.71%   +0.09%     
==========================================
  Files          12       12              
  Lines        1917     1926       +9     
==========================================
+ Hits          472      476       +4     
- Misses       1379     1384       +5     
  Partials       66       66              

Impacted Files	Coverage Δ
sync.go	0.00% <0.00%> (ø)
handler.go	44.68% <100.00%> (+0.29%)	⬆️
merkletree/hasher.go	100.00% <100.00%> (ø)

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