add dockerfile of server

Dockerfile

@@ -0,0 +1,22 @@
+FROM golang:bullseye as cache
+WORKDIR /src
+COPY go.mod go.sum .
+RUN  env GOPROXY=https://goproxy.io go mod download
+
+FROM golang:bullseye as build-base
+COPY --from=cache /go/pkg/mod /go/pkg/mod
+COPY . /src/
+WORKDIR /src
+
+FROM build-base as build-server
+RUN  go build -o /bin/signal-server ./cmd/signal-server
+
+FROM debian:bullseye as runtime
+ENTRYPOINT /bin/signal-server
+
+FROM result as result-updated
+RUN  apt update && apt dist-upgrade --yes && apt clean
+
+FROM runtime as result
+COPY --from=build-server /bin/signal-server /bin/signal-server
+