Fix linting errors

[zivkovicmilos]

Description

This PR resolves the linting errors outlined in the latest version of golangci-lint, as well as switches the import parser to goimports instead of gofmt

Changes include

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the relevant labels
• I have updated the official documentation
• I have added sufficient documentation in code

Testing

• I have tested this code with the official test suite
• I have tested this code manually

[Kourin1996]

LGTM

[codecov]

Codecov Report

Merging #675 (1fa3f31) into develop (39a6abd) will increase coverage by 0.00%.
The diff coverage is 59.18%.

@@           Coverage Diff            @@
##           develop     #675   +/-   ##
========================================
  Coverage    48.65%   48.66%           
========================================
  Files          112      112           
  Lines        15364    15363    -1     
========================================
  Hits          7476     7476           
+ Misses        7254     7253    -1     
  Partials       634      634           

Impacted Files	Coverage Δ
blockchain/subscription.go	72.00% <ø> (ø)
blockchain/testing.go	59.29% <ø> (ø)
consensus/ibft/consensus.go	0.00% <ø> (ø)
consensus/ibft/consensus_backend.go	0.00% <0.00%> (ø)
consensus/ibft/ibft.go	4.00% <0.00%> (ø)
consensus/ibft/pos.go	0.00% <ø> (ø)
consensus/ibft/sign.go	64.58% <ø> (ø)
consensus/ibft/verifier.go	0.00% <0.00%> (ø)
contracts/staking/query.go	71.42% <ø> (ø)
jsonrpc/errors.go	41.66% <ø> (ø)
... and 23 more

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