feat: initialize transactionMu in NewAdapterByDBUseTableName (#237)

constructor NewAdapterByDBUseTableName should initialize transactionMu,
otherwise it will ~~panic~~ blocked due to that cas when calling Transaction

Besides, a few other constructors also depend on NewAdapterByDBUseTableName,
if transactionMu is not initialized in NewAdapterByDBUseTableName,
it will blocked as well.

Besides, why not consider use sync.Once to initialize transactionMu?

adapter.go

@@ -22,7 +22,6 @@ import (
 	"runtime"
 	"strings"
 	"sync"
-	"sync/atomic"
 
 	"github.com/casbin/casbin/v2"
 	"github.com/casbin/casbin/v2/model"
@@ -84,7 +83,7 @@ type Adapter struct {
 	db             *gorm.DB
 	isFiltered     bool
 	transactionMu  *sync.Mutex
-	muInitialize   atomic.Bool
+	muInitialize   sync.Once
 }
 
 // finalizer is the destructor for Adapter.
@@ -200,8 +199,9 @@ func NewAdapterByDBUseTableName(db *gorm.DB, prefix string, tableName string) (*
 	}
 
 	a := &Adapter{
-		tablePrefix: prefix,
-		tableName:   tableName,
+		tablePrefix:   prefix,
+		tableName:     tableName,
+		transactionMu: &sync.Mutex{},
 	}
 
 	a.db = db.Scopes(a.casbinRuleTable()).Session(&gorm.Session{Context: db.Statement.Context})
@@ -259,9 +259,10 @@ func NewFilteredAdapter(driverName string, dataSourceName string, params ...inte
 // Casbin will not automatically call LoadPolicy() for a filtered adapter.
 func NewFilteredAdapterByDB(db *gorm.DB, prefix string, tableName string) (*Adapter, error) {
 	adapter := &Adapter{
-		tablePrefix: prefix,
-		tableName:   tableName,
-		isFiltered:  true,
+		tablePrefix:   prefix,
+		tableName:     tableName,
+		isFiltered:    true,
+		transactionMu: &sync.Mutex{},
 	}
 	adapter.db = db.Scopes(adapter.casbinRuleTable()).Session(&gorm.Session{Context: db.Statement.Context})
 
@@ -692,12 +693,11 @@ func (a *Adapter) AddPolicies(sec string, ptype string, rules [][]string) error
 func (a *Adapter) Transaction(e casbin.IEnforcer, fc func(casbin.IEnforcer) error, opts ...*sql.TxOptions) error {
 	// ensure the transactionMu is initialized
 	if a.transactionMu == nil {
-		for a.muInitialize.CompareAndSwap(false, true) {
+		a.muInitialize.Do(func() {
 			if a.transactionMu == nil {
 				a.transactionMu = &sync.Mutex{}
 			}
-			a.muInitialize.Store(false)
-		}
+		})
 	}
 	// lock the transactionMu to ensure the transaction is thread-safe
 	a.transactionMu.Lock()
@@ -706,15 +706,15 @@ func (a *Adapter) Transaction(e casbin.IEnforcer, fc func(casbin.IEnforcer) erro
 	oriAdapter := a.db
 	// reload policy from database to sync with the transaction
 	defer func() {
-		e.SetAdapter(&Adapter{db: oriAdapter})
+		e.SetAdapter(&Adapter{db: oriAdapter, transactionMu: a.transactionMu})
 		err = e.LoadPolicy()
 		if err != nil {
 			panic(err)
 		}
 	}()
 	copyDB := *a.db
 	tx := copyDB.Begin(opts...)
-	b := &Adapter{db: tx}
+	b := &Adapter{db: tx, transactionMu: a.transactionMu}
 	// copy enforcer to set the new adapter with transaction tx
 	copyEnforcer := e
 	copyEnforcer.SetAdapter(b)