fix: update docker file

Dockerfile

@@ -1,7 +1,14 @@
-FROM dart:2.19.1
+FROM dart:2.19.1 as builder
+WORKDIR /app
 COPY pubspec.yaml pubspec.lock ./
 RUN dart pub get 
 COPY . .
-RUN dart compile exe bin/cli.dart -o server
+RUN dart compile exe bin/cli.dart
 RUN chmod 777 server
-ENTRYPOINT [ "./server" ]
+
+# copy server file to basic image to run the app
+FROM ubuntu:18.04
+WORKDIR /app
+COPY --from=builder /app/server .
+
+CMD [ "./server" ]

pubspec.yaml

@@ -7,7 +7,7 @@ environment:
   sdk: '>=2.17.5 <3.0.0'
 
 dependencies:
-  alfred:
+  alfred: ^1.0.0+1
 
 dev_dependencies:
   lints: ^2.0.0