dialect: support for begintx in debug mode (#1176)

examples/privacyadmin/ent/client.go

@@ -81,7 +81,9 @@ func (c *Client) BeginTx(ctx context.Context, opts *sql.TxOptions) (*Tx, error)
 	if _, ok := c.driver.(*txDriver); ok {
 		return nil, fmt.Errorf("ent: cannot start a transaction within a transaction")
 	}
-	tx, err := c.driver.(*sql.Driver).BeginTx(ctx, opts)
+	tx, err := c.driver.(interface {
+		BeginTx(context.Context, *sql.TxOptions) (dialect.Tx, error)
+	}).BeginTx(ctx, opts)
 	if err != nil {
 		return nil, fmt.Errorf("ent: starting a transaction: %v", err)
 	}