Migrate from dep to go mod

[eloyekunle]

Since Go 1.11 there is a new way to structure packages, which don't require the project to live under $GOPATH, and provides version management.

go mod could superseed dep, given it is builtin on the core tooling of the language and requires less dependencies to contribute.

This commit follows the migration instructions to adopt go mod.

[maciaszczykm]

Great! Looking forward to merging this. Could you take a look at the errors in the CI?

[maciaszczykm]

Master is broken, not this PR. You can take a look on it if you have some time.

cc @floreks @jeefy

[shu-mutou]

At least, before tests or building image that use vendor directory, we need to set GO111MODULE and run go mod like follow.

export GO111MODULE=on
go mod download
go mod vendor

We can run almost tests on local. See https://github.com/kubernetes/dashboard/wiki/Getting-started#to-run-npm-commands-as-you-want . It's almost same as on travis. Please run test locally at first.

[eloyekunle]

The backend tests pass currently when I run it locally. This current broken build is from master, not the go modules migration.

[floreks]

Rebase please to fix travis.

[codecov]

Codecov Report

Merging #3878 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3878      +/-   ##
==========================================
- Coverage   46.57%   46.56%   -0.02%     
==========================================
  Files         173      173              
  Lines        8066     8066              
  Branches       59       59              
==========================================
- Hits         3757     3756       -1     
- Misses       4079     4080       +1     
  Partials      230      230

Impacted Files	Coverage Δ
...p/backend/integration/metric/common/aggregation.go	89.09% <0%> (-1.82%)	⬇️

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[eloyekunle]

I've rebased @floreks

[shu-mutou]

For now, I couldn't find why vendor directory [1] that were used by tests and build becomes unnecessary. But we need to clean up the use of vendor directory, if vendor is really unused. Could you clean up them?
[1] https://github.com/kubernetes/dashboard/search?q=vendor&unscoped_q=vendor

[maciaszczykm]

/approve

Please solve conflicts and answer to @shu-mutou comment.

[eloyekunle]

@shu-mutou The vendor directory is still used during build and is still necessary. By running go mod vendor locally, the appropriate packages are added to the vendor directory.

[shu-mutou]

/lgtm
Great! And thank you for your answer. I think, we need to memo somewhere how to build container image, but I could confirm that we can launch the dashboard, the CI checks is passing and we can fix concerns later.

[k8s-ci-robot]

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This pull-request has been approved by: eloyekunle, maciaszczykm, shu-mutou

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