golang/go · error · PackageError

named files must be .go files: %s

Error message

named files must be .go files: %s

What it means

Returned by GoFilesPackage at line 3283. This function handles the `go run`/`go build` case where individual .go files are passed on the command line. Every argument must end in `.go`; the first one that does not causes a synthesized Package whose Error is this message and whose Name is the bad argument. The check is a pure suffix test on the file name.

Source

Thrown at src/cmd/go/internal/load/pkg.go:3283

		p.Internal.Ldflags = BuildLdflags.For(ld, p)
		p.Internal.Gccgoflags = BuildGccgoflags.For(ld, p)
	}
}

// GoFilesPackage creates a package for building a collection of Go files
// (typically named on the command line). The target is named p.a for
// package p or named after the first Go file for package main.
func GoFilesPackage(ld *modload.Loader, ctx context.Context, opts PackageOpts, gofiles []string) *Package {
	modload.Init(ld)

	for _, f := range gofiles {
		if !strings.HasSuffix(f, ".go") {
			pkg := new(Package)
			pkg.Internal.Local = true
			pkg.Internal.CmdlineFiles = true
			pkg.Name = f
			pkg.Error = &PackageError{
				Err: fmt.Errorf("named files must be .go files: %s", pkg.Name),
			}
			pkg.Incomplete = true
			return pkg
		}
	}

	var stk ImportStack
	ctxt := cfg.BuildContext
	ctxt.UseAllFiles = true

	// Synthesize fake "directory" that only shows the named files,
	// to make it look like this is a standard package or
	// command directory. So that local imports resolve
	// consistently, the files must all be in the same directory.
	var dirent []fs.FileInfo
	var dir string
	for _, file := range gofiles {
		fi, err := fsys.Stat(file)

View on GitHub (pinned to b6b368adc5)

Solutions

1. Append `.go` to the argument: `go run main.go`.
2. Filter the file list to only `*.go` before passing it to `go run`/`go build`.
3. If you meant to build a package, pass the import path or package directory instead of individual files.

Example fix

# before
go run main
# after
go run main.go

// Validate that every file argument ends in .go before invoking go run/build.
package argcheck

import (
	"errors"
	"strings"
)

func AllArgsAreGoFiles(files []string) error {
	for _, f := range files {
		if !strings.HasSuffix(f, ".go") {
			return errors.New("not a .go file: " + f)
		}
	}
	return nil
}

When it happens

Trigger: Invoking `go run foo.txt`, `go build main`, `go vet app.go README.md`, or passing a directory/binary/script as if it were a .go file. Even an empty extension (`go run README`) fails.

Common situations: Typing `go run main` instead of `go run main.go`; shell glob expanding to include a non-.go file; passing a build script by mistake; tutorials that drop the extension.

Related errors

• tool %q is ambiguous; choose one of:
• C compiler %q not found: %v
• Fortran source files not allowed when not using cgo or SWIG:
• main package is in repository %q but current directory is in
• main module is in repository %q but current directory is in

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/68361f8ca83a1419. Report an issue: GitHub.