add go.mod files to testdata directories

[jchunkins]

Description

add go.mod files as workaround for "go get" failures on directories that contain colon characters. See example in issue for error that is generated. This is based on the workaround discussed in golang/go#41402 (comment)

Fixes # 344

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

1. Create a go project
2. execute a go get command (e.g. `go get github.com/openshift/oc-mirror@97db160a1ac084c03c8266649c9e2fe140b631b8)
3. With the workaround in place you won't get invalid char ':' errors

Test Configuration:

• Firmware version:
• Hardware:
• Toolchain:
• SDK:

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[openshift-ci]

@jchunkins: all tests passed!

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[lmzuccarelli]

/lgtm

[lmzuccarelli]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jchunkins, lmzuccarelli

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