fix(trader): add mutex to prevent race condition in Meta refresh (#796)

* fix(trader): add mutex to prevent race condition in Meta refresh (issue #742)
**問題**：
根據 issue #742 審查標準，發現 BLOCKING 級別的並發安全問題：
- refreshMetaIfNeeded() 中的 `t.meta = meta` 缺少並發保護
- 多個 goroutine 同時調用 OpenLong/OpenShort 會造成競態條件
**修復**：
1. 添加 sync.RWMutex 保護 meta 字段
2. refreshMetaIfNeeded() 使用寫鎖保護 meta 更新
3. getSzDecimals() 使用讀鎖保護 meta 訪問
**符合標準**：
- issue #742: "並發安全問題需使用 sync.Once 等機制"
- 使用 RWMutex 實現讀寫分離，提升並發性能
Co-Authored-By: tinkle-community <tinklefund@gmail.com>
* test(trader): add comprehensive race condition tests for meta field mutex protection
- Test concurrent reads (100 goroutines accessing getSzDecimals)
- Test concurrent read/write (50 readers + 10 writers simulating meta refresh)
- Test nil meta edge case (returns default value 4)
- Test valid meta with multiple coins (BTC, ETH, SOL)
- Test massive concurrency (1000 iterations with race detector)
All 5 test cases passed, including -race verification with no data races detected.
Co-Authored-By: tinkle-community <tinklefund@gmail.com>
---------
Co-authored-by: ZhouYongyou <128128010+zhouyongyou@users.noreply.github.com>
Co-authored-by: tinkle-community <tinklefund@gmail.com>

trader/hyperliquid_trader_race_test.go

@@ -0,0 +1,192 @@
+package trader
+
+import (
+	"context"
+	"sync"
+	"testing"
+
+	"github.com/sonirico/go-hyperliquid"
+)
+
+// TestMetaConcurrentAccess tests that concurrent access to meta field is safe
+func TestMetaConcurrentAccess(t *testing.T) {
+	// Create a HyperliquidTrader instance with meta initialized
+	trader := &HyperliquidTrader{
+		ctx: context.Background(),
+		meta: &hyperliquid.Meta{
+			Universe: []hyperliquid.AssetInfo{
+				{Name: "BTC", SzDecimals: 5},
+				{Name: "ETH", SzDecimals: 4},
+			},
+		},
+		metaMutex: sync.RWMutex{},
+	}
+
+	// Number of concurrent goroutines
+	concurrency := 100
+	var wg sync.WaitGroup
+
+	// Test concurrent reads (getSzDecimals)
+	for i := 0; i < concurrency; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			// This should not cause race conditions
+			decimals := trader.getSzDecimals("BTC")
+			if decimals != 5 {
+				t.Errorf("Expected decimals 5, got %d", decimals)
+			}
+		}()
+	}
+
+	wg.Wait()
+}
+
+// TestMetaConcurrentReadWrite tests concurrent reads and writes to meta field
+func TestMetaConcurrentReadWrite(t *testing.T) {
+	trader := &HyperliquidTrader{
+		ctx: context.Background(),
+		meta: &hyperliquid.Meta{
+			Universe: []hyperliquid.AssetInfo{
+				{Name: "BTC", SzDecimals: 5},
+			},
+		},
+		metaMutex: sync.RWMutex{},
+	}
+
+	var wg sync.WaitGroup
+	concurrency := 50
+
+	// Concurrent readers
+	for i := 0; i < concurrency; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			trader.getSzDecimals("BTC")
+		}()
+	}
+
+	// Concurrent writers (simulating meta refresh)
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func(iteration int) {
+			defer wg.Done()
+			// Simulate meta update
+			trader.metaMutex.Lock()
+			trader.meta = &hyperliquid.Meta{
+				Universe: []hyperliquid.AssetInfo{
+					{Name: "BTC", SzDecimals: 5 + iteration%3},
+					{Name: "ETH", SzDecimals: 4},
+				},
+			}
+			trader.metaMutex.Unlock()
+		}(i)
+	}
+
+	wg.Wait()
+
+	// Verify meta is not nil after all operations
+	trader.metaMutex.RLock()
+	if trader.meta == nil {
+		t.Error("Meta should not be nil after concurrent operations")
+	}
+	trader.metaMutex.RUnlock()
+}
+
+// TestGetSzDecimals_NilMeta tests getSzDecimals with nil meta
+func TestGetSzDecimals_NilMeta(t *testing.T) {
+	trader := &HyperliquidTrader{
+		meta:      nil,
+		metaMutex: sync.RWMutex{},
+	}
+
+	// Should return default value 4 when meta is nil
+	decimals := trader.getSzDecimals("BTC")
+	expectedDecimals := 4
+
+	if decimals != expectedDecimals {
+		t.Errorf("Expected default decimals %d for nil meta, got %d", expectedDecimals, decimals)
+	}
+}
+
+// TestGetSzDecimals_ValidMeta tests getSzDecimals with valid meta
+func TestGetSzDecimals_ValidMeta(t *testing.T) {
+	trader := &HyperliquidTrader{
+		meta: &hyperliquid.Meta{
+			Universe: []hyperliquid.AssetInfo{
+				{Name: "BTC", SzDecimals: 5},
+				{Name: "ETH", SzDecimals: 4},
+				{Name: "SOL", SzDecimals: 3},
+			},
+		},
+		metaMutex: sync.RWMutex{},
+	}
+
+	tests := []struct {
+		coin            string
+		expectedDecimals int
+	}{
+		{"BTC", 5},
+		{"ETH", 4},
+		{"SOL", 3},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.coin, func(t *testing.T) {
+			decimals := trader.getSzDecimals(tt.coin)
+			if decimals != tt.expectedDecimals {
+				t.Errorf("For coin %s, expected decimals %d, got %d", tt.coin, tt.expectedDecimals, decimals)
+			}
+		})
+	}
+}
+
+// TestMetaMutex_NoRaceCondition tests that using -race detector finds no issues
+// Run with: go test -race -run TestMetaMutex_NoRaceCondition
+func TestMetaMutex_NoRaceCondition(t *testing.T) {
+	trader := &HyperliquidTrader{
+		ctx: context.Background(),
+		meta: &hyperliquid.Meta{
+			Universe: []hyperliquid.AssetInfo{
+				{Name: "BTC", SzDecimals: 5},
+				{Name: "ETH", SzDecimals: 4},
+			},
+		},
+		metaMutex: sync.RWMutex{},
+	}
+
+	var wg sync.WaitGroup
+	iterations := 1000
+
+	// Massive concurrent reads
+	for i := 0; i < iterations; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			trader.getSzDecimals("BTC")
+			trader.getSzDecimals("ETH")
+		}()
+	}
+
+	// Concurrent writes
+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+		go func(idx int) {
+			defer wg.Done()
+			trader.metaMutex.Lock()
+			trader.meta = &hyperliquid.Meta{
+				Universe: []hyperliquid.AssetInfo{
+					{Name: "BTC", SzDecimals: 5},
+					{Name: "ETH", SzDecimals: 4},
+					{Name: "SOL", SzDecimals: 3},
+				},
+			}
+			trader.metaMutex.Unlock()
+		}(i)
+	}
+
+	wg.Wait()
+
+	// If we reach here without race detector errors, the test passes
+	t.Log("No race conditions detected in concurrent meta access")
+}