Fix module cache in staging.Dockerfile

staging.Dockerfile

@@ -23,15 +23,18 @@ FROM base AS cache
 ARG VERSION
 COPY --from=tdlib /compiled/ /usr/local/
 WORKDIR /src
-RUN --mount=type=cache,target=/go \
-    --mount=type=cache,target=/root/.cache/go-build \
+RUN go env -w GOCACHE=/go-cache
+RUN go env -w GOMODCACHE=/gomod-cache
+RUN --mount=type=cache,target=/gomod-cache \
     --mount=type=bind,source=./,target=/src \
-    go get
+    go mod download
 
 FROM cache AS build
 ARG MAKEOPTS
 WORKDIR /src
 RUN --mount=type=bind,source=./,target=/src,rw \
+    --mount=type=cache,target=/go-cache \
+    --mount=type=cache,target=/gomod-cache \
     --mount=type=cache,destination=/src/release \
     make ${MAKEOPTS}