Modernize Your Go Codebase with the Revamped `go fix` in Go 1.26

The Go 1.26 release introduces a fully rewritten go fix subcommand, designed to make modernizing your Go code easier than ever. This tool applies a suite of analyzers that automatically detect and update code patterns, often leveraging newer language and library features. In this article, we'll walk through how to use go fix to upgrade your projects, explore the built-in fixers, and peek under the hood at the infrastructure that powers this self-service analysis system.

Getting Started with go fix

Like go build and go vet, go fix accepts package patterns. To fix all packages under the current directory, simply run:

$ go fix ./...

On success, the command silently updates your source files. It intelligently skips generated files, since the proper fix would be to change the generator logic itself. To make life easier for code reviewers, we recommend starting from a clean git state before running go fix — that way the resulting commit contains only the automated changes.

Previewing Changes with -diff

Before applying fixes, you can see what go fix would do using the -diff flag:

$ go fix -diff ./...

This prints a diff of each proposed change. For example, it might transform:

eq := strings.IndexByte(pair, '=')
result[pair[:eq]] = pair[1+eq:]

into the more robust:

before, after, _ := strings.Cut(pair, "=")

Available Fixers

You can list all registered analyzers by running go tool fix help. Here are some of the most useful ones:

• any — replaces interface{} with any, the modern alias.
• buildtag — checks and updates //go:build and // +build directives.
• fmtappendf — replaces []byte(fmt.Sprintf(...)) with the more efficient fmt.Appendf.
• forvar — removes redundant re-declarations of loop variables. Before Go 1.22, it was common to shadow loop variables to avoid closure bugs; this fixer safely removes those shadow variables now that the language semantics have changed.
• hostport — validates address formats passed to net.Dial and similar functions.
• inline — applies fixes based on //go:fix inline comment directives.
• mapsloop — replaces explicit loops over maps with calls to the maps package, making code more readable.
• minmax — simplifies if/else chains into calls to min or max built-ins.

To get detailed documentation for a specific analyzer, use go tool fix help <name>. For instance:

$ go tool fix help forvar

Infrastructure and Self-Service Analysis

The rewritten go fix isn't just a collection of one-off patches — it's built on a robust infrastructure that allows module maintainers and organizations to define their own analyzers. This “self-service” approach means you can encode team-specific guidelines, best practices, or migration recipes directly into your development workflow.

Under the hood, each fixer is an analyzer that reports findings and suggests replacements. The tool applies them across your codebase, respecting build constraints and generation markers. As the ecosystem evolves, the Go team plans to add more fixers, and community contributions are welcome.

Conclusion

The revamped go fix is a powerful ally in keeping your Go code clean, idiomatic, and up-to-date. By running it regularly — especially after upgrading to a new Go release — you ensure your codebase benefits from the latest improvements without manual effort. Start with go fix -diff ./... to preview changes, then commit and enjoy your modernized code.