Update Dockerfile

deployment/Dockerfile

@@ -4,7 +4,10 @@ ENV GO111MODULE=on
 ENV GOPATH=/root/go
 RUN mkdir -p /root/go/src
 COPY dyndns /root/go/src/dyndns
-RUN cd /root/go/src/dyndns && go mod download && GOOS=linux go build -o /root/go/bin/dyndns && go test -v
+RUN cd /root/go/src/dyndns
+RUN go mod download
+RUN go mod verify
+RUN GOOS=linux go build -o /root/go/bin/dyndns && go test -v
 
 FROM debian:bullseye-slim