remove unnecessary error return

I was running "golangci-lint" and found this two warnings

internal/checker/checker.go:135:18: (*Checker).LoadIndex$3 - result 0 (error) is always nil (unparam)
        final := func() error {
                        ^
internal/repository/repository.go:457:18: (*Repository).LoadIndex$3 - result 0 (error) is always nil (unparam)
        final := func() error {
                        ^

It turns out that these functions are used only in "RunWorkers(...)",
which is used only two times in whole project right after this "final"
functions.
And because these "final" functions always return "nil", I've
descided, that it would be better to remove requriments for "final" func
to return error to avoid magick "return nil" at their end.

internal/checker/checker.go

@@ -132,9 +132,8 @@ func (c *Checker) LoadIndex(ctx context.Context) (hints []error, errs []error) {
 	}
 
 	// final closes indexCh after all workers have terminated
-	final := func() error {
+	final := func() {
 		close(resultCh)
-		return nil
 	}
 
 	// run workers on ch

internal/repository/repository.go

@@ -454,9 +454,8 @@ func (r *Repository) LoadIndex(ctx context.Context) error {
 	}
 
 	// final closes indexCh after all workers have terminated
-	final := func() error {
+	final := func() {
 		close(indexCh)
-		return nil
 	}
 
 	// run workers on ch

internal/repository/worker_group.go

@@ -10,7 +10,7 @@ import (
 // After all workers have terminated, finalFunc is run. If an error occurs in
 // one of the workers, it is returned. FinalFunc is always run, regardless of
 // any other previous errors.
-func RunWorkers(ctx context.Context, count int, workerFunc, finalFunc func() error) error {
+func RunWorkers(ctx context.Context, count int, workerFunc func() error, finalFunc func()) error {
 	wg, ctx := errgroup.WithContext(ctx)
 
 	// run workers
@@ -22,14 +22,12 @@ func RunWorkers(ctx context.Context, count int, workerFunc, finalFunc func() err
 	err := wg.Wait()
 
 	// make sure finalFunc is run
-	finalErr := finalFunc()
+	finalFunc()
 
-	// if the workers returned an error, return it to the caller (disregarding
-	// any error from finalFunc)
+	// if the workers returned an error, return it to the caller
 	if err != nil {
 		return err
 	}
 
-	// if not, return the value finalFunc returned
-	return finalErr
+	return nil
 }