fix: examples/demo/server/Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE315-OPENSSL-5788364
- https://snyk.io/vuln/SNYK-ALPINE315-OPENSSL-5788364

examples/demo/server/Dockerfile

@@ -16,6 +16,6 @@ WORKDIR /app/
 COPY . .
 RUN go env -w GOPROXY=direct
 RUN CGO_ENABLED=0 go build -o main main.go
-FROM alpine:3.15
+FROM alpine:3.16
 COPY --from=build /app/main  /app/main
 CMD ["/app/main"]