Use efficient APIs and simplify loops

Minor refactors across the codebase to improve readability and use more efficient APIs: replace fmt.Sprintf+base64 encoding with fmt.Appendf when building Shadowsocks userInfo; compute elapsed using max(now-prev.at, window) to simplify logic; use strings.SplitSeq for splitting in two places; simplify test and goroutine loops to range-based iterations and use errgroup's Go helper; and align/clean up struct field formatting and test map literals. Mostly stylistic/efficiency changes with no intended behavior changes.

internal/xray/log_writer_race_test.go

@@ -16,18 +16,18 @@ func TestLogWriterLastLineConcurrent(t *testing.T) {
 	var wg sync.WaitGroup
 	wg.Add(writers + readers)
 
-	for i := 0; i < writers; i++ {
+	for range writers {
 		go func() {
 			defer wg.Done()
-			for j := 0; j < iterations; j++ {
+			for range iterations {
 				_, _ = lw.Write([]byte("2024/01/01 00:00:00.000000 [Info] connection accepted"))
 			}
 		}()
 	}
-	for i := 0; i < readers; i++ {
+	for range readers {
 		go func() {
 			defer wg.Done()
-			for j := 0; j < iterations; j++ {
+			for range iterations {
 				_ = lw.LastLine()
 			}
 		}()

internal/xray/process_race_test.go

@@ -19,9 +19,7 @@ func TestProcessLifecycleFieldsRaceSafe(t *testing.T) {
 	stop := make(chan struct{})
 
 	// Writer: churn cmd/done/exitErr like Start + waitForCommand.
-	wg.Add(1)
-	go func() {
-		defer wg.Done()
+	wg.Go(func() {
 		for {
 			select {
 			case <-stop:
@@ -34,13 +32,11 @@ func TestProcessLifecycleFieldsRaceSafe(t *testing.T) {
 			p.mu.Unlock()
 			p.setExitErr(errors.New("boom"))
 		}
-	}()
+	})
 
 	// Readers: the concurrent status getters.
-	for i := 0; i < 4; i++ {
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
+	for range 4 {
+		wg.Go(func() {
 			for {
 				select {
 				case <-stop:
@@ -51,7 +47,7 @@ func TestProcessLifecycleFieldsRaceSafe(t *testing.T) {
 				_ = p.GetErr()
 				_ = p.GetResult()
 			}
-		}()
+		})
 	}
 
 	time.Sleep(50 * time.Millisecond)