What causes "cannot find package in: %s" in golang/go?

Re-sync the module: `go mod download ` or `go mod vendor` (if vendored).

cannot find package in: %s

Error message

cannot find package in:
	%s

What it means

Stored as a string on rawPackage.error during importRaw when the directory targeted by reldir does not exist on disk. absdir is filepath.Join(modroot, reldir); isDir(absdir) returns false, so the package is reported as not found. Note the error is stored as its .Error() string (not an error value), preserving partial-info semantics for the eventual build.Package.

Source

Thrown at src/cmd/go/internal/modindex/scan.go:192

}

// importRaw fills the rawPackage from the package files in srcDir.
// dir is the package's path relative to the modroot.
func importRaw(modroot, reldir string) *rawPackage {
	p := &rawPackage{
		dir: reldir,
	}

	absdir := filepath.Join(modroot, reldir)

	// We still haven't checked
	// that p.dir directory exists. This is the right time to do that check.
	// We can't do it earlier, because we want to gather partial information for the
	// non-nil *build.Package returned when an error occurs.
	// We need to do this before we return early on FindOnly flag.
	if !isDir(absdir) {
		// package was not found
		p.error = fmt.Errorf("cannot find package in:\n\t%s", absdir).Error()
		return p
	}

	entries, err := fsys.ReadDir(absdir)
	if err != nil {
		p.error = err.Error()
		return p
	}

	fset := token.NewFileSet()
	for _, d := range entries {
		if d.IsDir() {
			continue
		}
		if d.Type()&fs.ModeSymlink != 0 {
			if isDir(filepath.Join(absdir, d.Name())) {
				// Symlinks to directories are not source files.
				continue

View on GitHub (pinned to b6b368adc5)

Solutions

Re-sync the module: `go mod download <module>` or `go mod vendor` (if vendored).
Verify replace directives in go.mod still point at existing local directories.
Clear the cache and re-resolve: `go clean -modcache && go mod download`.
Confirm the directory has not been git-cleaned or .gitignored out of the working copy.

Defensive patterns

Strategy: validation

Validate before calling

// Verify the directory exists before triggering importRaw.
func dirExistsUnderModroot(modroot, reldir string) bool {
    info, err := os.Stat(filepath.Join(modroot, reldir))
    return err == nil && info.IsDir()
}

Try / catch

// On 'cannot find package in', refresh the cache or re-vendor once and retry.
pkg, err := buildImport(modroot, reldir)
if err != nil && strings.Contains(err.Error(), "cannot find package in:") {
    _ = refreshModule(modroot) // go mod download / vendor
    pkg, err = buildImport(modroot, reldir)
}

Prevention

Run `go mod verify` and `go mod vendor` after dependency changes.
Keep replace directives pointing at directories that actually exist.
Do not delete files under GOMODCACHE manually.

When it happens

Trigger: importRaw(modroot, reldir) when <modroot>/<reldir> is missing — the index references a directory that has since been deleted, or reldir came from an outdated cache. Also reached when building against a module whose source tree was pruned.

Common situations: Module cache entry was partially deleted; vendor/ tree is out of date relative to go.mod; a replace directive points at a local path that was removed; manual edits to GOMODCACHE.

Related errors

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/3a6e774e55cb3cc8. Report an issue: GitHub.