chore: add multistage build to optimize the image size

Dockerfile

@@ -6,6 +6,9 @@ COPY . .
 
 RUN apk add build-base && cd server && go mod download && go build && chmod 777 server && ls -l
 
+FROM alpine:latest
+RUN apk --no-cache add ca-certificates
+WORKDIR /root/
+COPY --from=builder /app/server/server .
 EXPOSE 8080
-
-ENTRYPOINT [ "/app/server/server" ]
+CMD [ "./server" ]