Fix config module for unit test

Signed-off-by: Asai Neko <sugar@sne.moe>

config.default.yaml

@@ -0,0 +1,11 @@
+server:
+    address: :8000
+    debug_mode: false
+    file_logger: false
+    jwt_secret: someting
+database:
+    type: postgres
+    host: 127.0.0.1
+    name: postgres
+    username: postgres
+    password: postgres