Go Version Manager

Go Version Manager

Choose the project-compatible Go toolchain before changing dependencies. Prefer the machine's existing goenv installation for real version switching. Fall back to explicit binary paths when no supported version manager is available.

Workflow

1. Read go.mod completely enough to identify go, toolchain, and replace directives.
2. Run .agents/skills/go-version-manager/scripts/go-version-manager.sh requirement <project-dir>, manager, and list.
3. Run .agents/skills/go-version-manager/scripts/go-version-manager.sh select <project-dir> to choose an installed binary.
4. Confirm the selected binary with <go-binary> version and <go-binary> env GOROOT GOTOOLCHAIN GOPATH GOMODCACHE GOCACHE.
5. Choose the switching scope:
   • For one command, use the script's exec command. With goenv, it sets GOENV_VERSION only for that command.
   • For the current terminal, run the command printed by shell-command (normally goenv shell <version>).
   • For a repository-persistent selection, use switch-local; this runs goenv local <version> and writes .go-version, so do it only when the user authorizes a repository change.
   • Change goenv global only when the user explicitly requests a machine-wide default change.
6. Review git diff -- go.mod go.sum after any module command.
7. Report the selected version, commands run, dependency changes, and verification result.

Selection rules

• Prefer an exact toolchain goX.Y.Z installation.
• Otherwise prefer the highest installed patch within the go X.Y minor line.
• Treat the go directive as the minimum language/toolchain requirement, not permission to upgrade the module directive.
• Use a newer minor only when no compatible same-minor installation exists, and explain the risk before module mutations.
• Do not set GOROOT for a normal Go installation; the selected go binary determines it.
• Do not rewrite /usr/local/go, system symlinks, shell profiles, or global PATH unless explicitly requested.
• Prefer an installed goenv and its installed versions. Honor another existing version manager (mise, asdf, g, gvm, Homebrew) when the repository already configures one. Do not introduce a second manager without approval.
• Do not automatically install a missing Go version. Report the missing version and ask before downloading or installing tools.

Module safety

• Never hand-edit go.sum to silence missing checksum errors.
• Run go mod tidy only with the selected project-compatible toolchain and when the task authorizes dependency-file changes.
• Prefer go mod download or the error's narrowly scoped go get module@version when only fetching an existing graph is required; inspect resulting diffs.
• Do not upgrade packages merely to compensate for using the wrong local Go version.
• Do not change the go or toolchain directive unless the user requests a project toolchain upgrade.
• Preserve unrelated user changes in go.mod and go.sum.

Diagnose common failures

• package slices is not in GOROOT: the active Go binary is older than Go 1.21. Switch toolchains before touching dependencies.
• missing go.sum entry: use the correct toolchain, then fetch or tidy the module graph; do not write checksums manually.
• Cache operation not permitted: keep the selected toolchain and redirect only writable caches, for example GOCACHE=<writable-temp-dir>. Redirect GOMODCACHE only when necessary because it can trigger full dependency downloads.
• Mock/test binary requires special flags or external services: distinguish compilation from execution. Use go test -c -o <temp-file> <package> for compile-only verification when package initialization prevents local execution.
• A command unexpectedly changes many dependencies: stop, inspect go version, go env GOTOOLCHAIN, module directives, and the diff before proceeding.

Verification ladder

Use the lowest sufficient level, then escalate by risk:

1. <go> version and <go> env ...
2. <go> mod verify
3. Targeted <go> test ./path/to/changed/package
4. Compile-only <go> test -c -o <temp-file> ./package
5. Broader go test ./... or project build command

If dependency downloads or writes outside the workspace require approval, request it rather than bypassing sandbox or network controls.

Script

Use .agents/skills/go-version-manager/scripts/go-version-manager.sh:

# Show go/toolchain requirements
.agents/skills/go-version-manager/scripts/go-version-manager.sh requirement /path/to/project

# List discovered Go binaries
.agents/skills/go-version-manager/scripts/go-version-manager.sh list

# Show which switching backend is available
.agents/skills/go-version-manager/scripts/go-version-manager.sh manager

# Print the selected Go binary
.agents/skills/go-version-manager/scripts/go-version-manager.sh select /path/to/project

# Execute with the selected binary
.agents/skills/go-version-manager/scripts/go-version-manager.sh exec /path/to/project -- test ./...

# Print the command that switches the current terminal
.agents/skills/go-version-manager/scripts/go-version-manager.sh shell-command /path/to/project

# Persist the selection for this repository (writes .go-version)
.agents/skills/go-version-manager/scripts/go-version-manager.sh switch-local /path/to/project

The script is read-only except for switch-local, which writes .go-version, and effects caused by the Go subcommand supplied to exec.