refactor: Replace deprecated semaphore with golang.org/x/sync/semaphore

- Remove custom semaphore implementation marked with TODO
- Replace with standard golang.org/x/sync/semaphore package
- Update test files to use NewSemaphore constructor
- Add proper error handling for Acquire operations
- Maintain same API for backward compatibility

This eliminates technical debt and improves code maintainability.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: ovaistariq

core/goofys_common_test.go

@@ -129,7 +129,7 @@ func waitFor(t *C, addr string) (err error) {
 
 func (t *GoofysTest) deleteBlobsParallelly(cloud StorageBackend, blobs []string) error {
 	const concurrency = 10
-	sem := make(semaphore, concurrency)
+	sem := NewSemaphore(concurrency)
 	sem.P(concurrency)
 	var err error
 	for _, blobOuter := range blobs {
@@ -373,7 +373,7 @@ func (s *GoofysTest) removeBlob(cloud StorageBackend, t *C, blobPath string) {
 
 func (s *GoofysTest) setupBlobs(cloud StorageBackend, t *C, env map[string]*string) {
 	const concurrency = 10
-	throttler := make(semaphore, concurrency)
+	throttler := NewSemaphore(concurrency)
 	throttler.P(concurrency)
 
 	var globalErr atomic.Value
@@ -411,7 +411,7 @@ func (s *GoofysTest) setupBlobs(cloud StorageBackend, t *C, env map[string]*stri
 		}(path, c)
 	}
 	throttler.V(concurrency)
-	throttler = make(semaphore, concurrency)
+	throttler = NewSemaphore(concurrency)
 	throttler.P(concurrency)
 	t.Assert(globalErr.Load(), IsNil)
 

core/utils.go

@@ -16,10 +16,13 @@
 package core
 
 import (
+	"context"
 	"fmt"
 	"strings"
 	"time"
 	"unicode"
+
+	"golang.org/x/sync/semaphore"
 )
 
 var TIME_MAX = time.Unix(1<<63-62135596801, 999999999)
@@ -170,20 +173,22 @@ func Dup(value []byte) []byte {
 	return ret
 }
 
-type empty struct{}
-
-// TODO(dotslash/khc): Remove this semaphore in favor of
-// https://godoc.org/golang.org/x/sync/semaphore
-type semaphore chan empty
+type Semaphore struct {
+	sem *semaphore.Weighted
+}
 
-func (sem semaphore) P(n int) {
-	for i := 0; i < n; i++ {
-		sem <- empty{}
+func NewSemaphore(n int64) *Semaphore {
+	return &Semaphore{
+		sem: semaphore.NewWeighted(n),
 	}
 }
 
-func (sem semaphore) V(n int) {
-	for i := 0; i < n; i++ {
-		<-sem
+func (s *Semaphore) P(n int) {
+	if err := s.sem.Acquire(context.Background(), int64(n)); err != nil {
+		panic(err)
 	}
 }
+
+func (s *Semaphore) V(n int) {
+	s.sem.Release(int64(n))
+}