check error number.

Author: shogo82148

connection_go18.go

@@ -78,7 +78,9 @@ func (mc *mysqlConn) beginReadOnly() (driver.Tx, error) {
 	}
 	err := mc.exec("START TRANSACTION READ ONLY")
 	if err != nil {
-		if _, ok := err.(*MySQLError); ok {
+		if err, ok := err.(*MySQLError); ok && err.Number == 1064 {
+			// Error 1064 ER_PARSE_ERROR
+			// It seems that your MySQL does not support READ ONLY transactions.
 			return nil, ErrReadOnlyTxNotSupported
 		}
 		return nil, err

driver_go18_test.go

@@ -487,7 +487,9 @@ func TestContextBeginReadOnly(t *testing.T) {
 
 		// INSERT queries fail in a READ ONLY transaction.
 		_, err = tx.ExecContext(ctx, "INSERT INTO test VALUES (1)")
-		if _, ok := err.(*MySQLError); !ok {
+		// Error 1792 ER_CANT_EXECUTE_IN_READ_ONLY_TRANSACTION
+		// https://dev.mysql.com/doc/refman/5.6/en/innodb-performance-ro-txn.html
+		if err, ok := err.(*MySQLError); !ok || err.Number != 1792 {
 			dbt.Errorf("expected MySQLError, got %v", err)
 		}