Modern Go

Write Go in one project-selected form. Use modern Go only inside the repository's compatibility, behavior, and policy boundaries.

Establish the contract

1. Read the nearest AGENTS.md and repository instructions.
2. Locate the applicable go.work and go.mod files.
3. Record the target Go version for each affected module.
4. Read the affected source, tests, callers, interfaces, and recent changes.
5. State the current behavior and the behavior that the task requires.

Do not use a feature only because the local toolchain accepts it. The affected module's declared Go version is the default compatibility boundary.

For a review or diagnosis, inspect and report. Do not edit unless the request includes a change.

Read modern Go guidance

Run the bundled modern-guidelines wrapper before you review or edit Go code. Resolve <skill-directory> to this installed skill's directory.

On Linux or macOS, run:

sh "<skill-directory>/scripts/run-tool.sh" list --file-path path/to/file.go

On Windows PowerShell, run:

& '<skill-directory>\scripts\run-tool.ps1' list --file-path path\to\file.go

The first run installs the pinned Modern Go Guidelines CLI in a user cache. Use the host's approval flow when the install needs network or write access.

If no target file exists, pass the known version:

sh "<skill-directory>/scripts/run-tool.sh" list --go-version 1.24

Read the complete output. Do not filter or truncate it. Older entries can still apply to the target version.

Request details only for a relevant guideline:

sh "<skill-directory>/scripts/run-tool.sh" explain guideline-id

If files use different module versions, run list once for each version. If the command is unavailable, use repository evidence and report the skipped guidance check.

Resolve the goago policy

Before a Go code change or review, inspect go.mod for this module tool:

tool github.com/agentstation/goago/cmd/goago

Use go tool goago when the module declares the tool. Use a global goago command only when repository instructions require it. Read the nearest .goago.yml or .goago.yaml when one exists.

A goago policy file is optional. The pinned goago version supplies built-in defaults when no policy file exists.

Do not install goago or add a policy unless the user requests adoption. If the goago Agent Skill is available, use its complete remediation workflow.

When the repository owns a goago command, discover the resolved policy before you choose a Go form:

go tool goago -list -format json

Use each rules[].enabled value as the active restriction set. Also read policy.ruleSource, policy.configPath, policy.tests, and policy.exclude. A built-in rule source is a complete policy, not a missing policy. A config rule source records the selected policy file.

An active goago restriction takes priority over a modern form. For example, do not use expression-based new when no-new-expr is active. Keep a generic operation as a package function when no-generic-methods is active.

If the module still pins github.com/agentstation/ago/cmd/ago, use go tool ago until the user requests migration. Read legacy .ago.yml and .ago.yaml policies too. The goago skill includes the migration procedure. Versions of ago before v0.2.0 do not include the policy JSON metadata.

Make the change

• Use the newest applicable form that the target version and policy accept.
• Keep new code consistent with the selected project policy.
• Prefer the simplest form that keeps control flow, ownership, and data visible.
• Preserve behavior, exported APIs, wire formats, and error identity unless the task changes them.
• Keep the smallest coherent change. Do not modernize unrelated code.
• Prefer the standard library when it provides the required contract.
• Keep ownership with the package or type that owns the domain concept.
• Do not edit generated, vendored, or third-party code directly.
• Add a regression test when an automated test can reproduce a defect.

Skip a relevant modern guideline only when it would fail to compile, change required behavior, or violate project policy. Read its explain output before you skip it.

Verify the result

1. Run gofmt on each changed handwritten Go file.
2. Run the affected package tests.
3. Run the repository's complete Go check when the task scope permits it.
4. Run race or platform checks when the changed behavior depends on them.
5. Run goago when the repository owns an available command.

Use the same goago command form that supplied the policy:

go tool goago -stale-ignores -format json ./...

Status 0 means the run completed without findings. Status 1 means the run found a violation or stale ignore. Status 2 means the run was incomplete. Read the JSON errors field before you change source after status 2.

Fix source when the selected goago policy reports a finding. Do not weaken the policy or add a suppression only to make the check pass.

Report the checks, results, skipped checks, and remaining uncertainty.