build: bump Go to v1.26.8

[FengyuanYin]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Updates the Go version from 1.26.7 to 1.26.8 in go.mod and the Go builder images used by the Dockerfiles, keeping the development and build toolchains consistent.

Which issue(s) this PR fixes:

Fixes #NONE

Special notes for your reviewer:

This is a patch-level Go toolchain update. No application behavior or dependencies are changed.

Does this PR introduce a user-facing change?:

NONE

[volcano-sh-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign hzxuzhonghu for approval. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.04%. Comparing base (5903457) to head (d251a92).
⚠️ Report is 7 commits behind head on main.
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #463      +/-   ##
==========================================
+ Coverage   59.98%   60.04%   +0.05%     
==========================================
  Files          36       36              
  Lines        3589     3589              
==========================================
+ Hits         2153     2155       +2     
+ Misses       1216     1215       -1     
+ Partials      220      219       -1     

Flag	Coverage Δ
unittests	60.04% <ø> (+0.05%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[acsoto]

I fixed e2e in #465

[RainbowMango]

/close
in favor of #465

[volcano-sh-bot]

@RainbowMango: Closed this PR.

Details

In response to this:

/close
in favor of #465

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[Copilot]

Copilot review overview

🟢 Approval recommended

All reviewed changes are consistent toolchain version updates with no unresolved issues.

Review effort: Lite
Findings: None

What changed in this PR

Updates the Go toolchain from 1.26.7 to 1.26.8 across module metadata and Docker builder images.

Changes:

• Bumps the go.mod Go version.
• Updates all three Docker builder image tags.
• No application behavior or dependency changes.

File	Description
go.mod	Updates the required Go version.
docker/​Dockerfile.router	Updates the router builder image.
docker/​Dockerfile.picod	Updates the PicoD builder image.
docker/​Dockerfile	Updates the workload manager builder image.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.