Add s3 test and Refactor

[hlts2]

Signed-off-by: hlts2 hiroto.funakoshi.hiroto@gmail.com

Description:

author review required*

I added test case for s3.
and I refactor s3 implementation.

• WHY:
  I can not make test because we need to actually connect s3.
  https://github.com/vdaas/vald/blob/master/internal/db/storage/blob/s3/s3.go#L69
  therefore I want to fix it

• WHAT

  • I fixed it to be able to mock based on global variables

Related Issue:

How Has This Been Tested?:

Environment:

• Go Version: 1.15.2
• Docker Version: 19.03.8
• Kubernetes Version: 1.18.2
• NGT Version: 1.12.1

Types of changes:

• Bug fix [type/bug]
• New feature [type/feature]
• Add tests [type/test]
• Security related changes [type/security]
• Add documents [type/documentation]
• Refactoring [type/refactoring]
• Update dependencies [type/dependency]
• Update benchmarks and performances [type/bench]
• Update CI [type/ci]

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

Checklist:

• I have read the CONTRIBUTING document.
• I have checked open Pull Requests for the similar feature or fixes?
• I have added tests and benchmarks to cover my changes.
• I have ensured all new and existing tests passed.
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly.

[vdaas-ci]

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• 🏷️ /label - add labels
• ⏪ /rebase - rebase master

[codecov]

Codecov Report

Merging #837 (d1b0f43) into master (638f8dc) will decrease coverage by 0.05%.
The diff coverage is 81.25%.

@@            Coverage Diff             @@
##           master     #837      +/-   ##
==========================================
- Coverage   18.62%   18.56%   -0.06%     
==========================================
  Files         422      423       +1     
  Lines       19572    19586      +14     
==========================================
- Hits         3645     3637       -8     
- Misses      15711    15734      +23     
+ Partials      216      215       -1     

Impacted Files	Coverage Δ
internal/db/storage/blob/s3/reader/option.go	100.00% <ø> (ø)
internal/db/storage/blob/s3/reader/reader_mock.go	62.50% <0.00%> (-37.50%)	⬇️
internal/db/storage/blob/s3/writer/option.go	100.00% <ø> (ø)
internal/db/storage/blob/s3/writer/writer_mock.go	0.00% <0.00%> (ø)
internal/db/storage/blob/s3/reader/reader.go	65.51% <83.33%> (-0.40%)	⬇️
internal/db/storage/blob/s3/s3.go	94.28% <92.30%> (+94.28%)	⬆️
internal/db/storage/blob/s3/option.go	100.00% <100.00%> (ø)
internal/db/storage/blob/s3/writer/writer.go	100.00% <100.00%> (ø)
internal/net/http/client/client.go	0.00% <0.00%> (-89.48%)	⬇️
internal/net/http/json/json.go	48.75% <0.00%> (-31.25%)	⬇️
... and 2 more

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[kevindiu]

LGTM but please fix @rinx comment.
I think it requires author review due to refactoring, please write it to the PR description if it is required.

[vdaas-ci]

[FORMAT] Updating license headers and formatting go codes triggered by vankichi.

[vdaas-ci]

[APPROVED] This PR is approved by vankichi.