specify version of Ubuntu

.github/workflows/php.yml

@@ -4,7 +4,7 @@ on: [push]
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
 
     env:
       MYSQL_DATABASE: monarc_common
@@ -18,6 +18,7 @@ jobs:
     - name: Start MariaDB and create databases
       uses: getong/mariadb-action@v1.1
       with:
+        mariadb version: '10.4.10' # Optional, default value is "latest". The version of the MariaDB
         mysql database: $MYSQL_DATABASE # Optional, default value is "test". The specified database which will be create
         mysql root password: $MYSQL_ROOT_PASSWORD # Required if "mysql user" is empty, default is empty. The root superuser password
         mysql user: $MYSQL_USER # Required if "mysql root password" is empty, default is empty. The superuser for the specified database. Can use secrets, too