go: update to 1.26

[nkryuchkov]

as per title

[greptile-apps]

Greptile Summary

This PR updates the Go toolchain from version 1.24 to 1.26 across the entire repository. The changes are comprehensive and consistent:

• All go.mod files updated to go 1.26 with toolchain directives removed
• Docker images updated from golang:1.24 to golang:1.26 with pinned SHA256 digest (already addressed in previous review thread)
• GitHub Actions workflows improved by switching from hardcoded go-version: "1.24.x" to go-version-file: go.mod, which automatically reads the version from go.mod and eliminates the need for manual updates in CI
• Documentation updated to reflect new minimum Go version requirement

The workflow changes represent a best practice improvement - using go-version-file ensures CI automatically stays in sync with the version specified in go.mod, preventing version drift between development and CI environments.

Confidence Score: 5/5

• This PR is safe to merge with no identified risks
• The changes are purely version updates with complete consistency across all files. The Go 1.26 upgrade is a straightforward version bump with no breaking changes to the codebase. Docker image digests are properly pinned for reproducibility. The workflow improvements using go-version-file are a best practice that will prevent future version drift.
• No files require special attention

Important Files Changed

Filename	Overview
go.mod	Updated Go version from 1.24.6 to 1.26, removed toolchain directive
ssvsigner/go.mod	Updated Go version from 1.24.6 to 1.26, removed toolchain directive
tool.mod	Updated Go version from 1.24.6 to 1.26, removed toolchain directive
Dockerfile.multiarch	Updated golang:1.24.6 to golang:1.26.0 with new SHA256 digest in base and runner stages
.github/workflows/unit-test.yml	Changed from hardcoded go-version to go-version-file: go.mod for dynamic version management
.github/workflows/full-test.yml	Changed from hardcoded go-version to go-version-file: go.mod for dynamic version management

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Go 1.24 → 1.26 Update] --> B[Module Files]
    A --> C[Docker Images]
    A --> D[CI Workflows]
    A --> E[Documentation]
    
    B --> B1[go.mod: 1.24.6 → 1.26]
    B --> B2[ssvsigner/go.mod: 1.24.6 → 1.26]
    B --> B3[tool.mod: 1.24.6 → 1.26]
    B --> B4[scripts/differ/go.mod: 1.24 → 1.26]
    B1 --> B5[Remove toolchain directive]
    B2 --> B5
    B3 --> B5
    
    C --> C1[Dockerfile: golang:1.24 → 1.26]
    C --> C2[Dockerfile.multiarch: golang:1.24.6 → 1.26.0]
    C --> C3[dev.Dockerfile: golang:1.24 → 1.26]
    C --> C4[tests.Dockerfile: golang:1.24 → 1.26]
    C --> C5[ssvsigner/Dockerfile: golang:1.24 → 1.26]
    C2 --> C6[Pin SHA256 digest]
    
    D --> D1[7 workflow files]
    D1 --> D2[go-version: 1.24.x]
    D2 --> D3[go-version-file: go.mod]
    D3 --> D4[Auto-sync with go.mod]
    
    E --> E1[DEV_GUIDE.md: >=1.24 → >=1.26]
    E --> E2[ssvsigner/e2e/README.md: 1.24+ → 1.26+]
    
    style A fill:#e1f5ff
    style B5 fill:#d4edda
    style C6 fill:#d4edda
    style D4 fill:#d4edda

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_{Last reviewed commit: ef0d068}

[greptile-apps]

_{18 files reviewed, 2 comments}

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[nkryuchkov]

@greptileai please review it again

[greptile-apps]

_{18 files reviewed, no comments}

_{Edit Code Review Agent Settings | Greptile}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.1%. Comparing base (20ffb01) to head (e1b5639).

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[iurii-ssv]

LGTM,

I'm wondering though if we should use Golang version-pinning everywhere (as we do in Dockerfile.multiarch) ?