Use Github Action and clean up code

[codecov[bot]]

Codecov Report

Merging #59 (8fe95ed) into master (3499a85) will increase coverage by 0.95%. The diff coverage is 65.00%.

@@            Coverage Diff             @@
##           master      #59      +/-   ##
==========================================
+ Coverage   75.80%   76.75%   +0.95%     
==========================================
  Files          10       10              
  Lines         248      370     +122     
==========================================
+ Hits          188      284      +96     
- Misses         35       59      +24     
- Partials       25       27       +2     

Impacted Files	Coverage Δ
block.go	73.07% <63.15%> (-26.93%)	:arrow_down:
network.go	100.00% <100.00%> (ø)
transaction.go	89.65% <0.00%> (-0.83%)	:arrow_down:
stat.go	100.00% <0.00%> (ø)
contract.go	100.00% <0.00%> (ø)
error_wrap.go	50.00% <0.00%> (ø)
client.go	54.78% <0.00%> (+0.13%)	:arrow_up:
helper.go	73.68% <0.00%> (+1.68%)	:arrow_up:
account.go	93.47% <0.00%> (+2.17%)	:arrow_up:
... and 1 more

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