optimize dockerfile

Dockerfile

@@ -1,11 +1,17 @@
-FROM rustlang/rust:nightly-slim
-RUN apt update; apt install -y libpq-dev
+# syntax=docker/dockerfile:1.4
 
+FROM rustlang/rust:nightly-slim AS builder
+RUN apt update; apt install -y libpq-dev
 WORKDIR /code
 COPY . .
-RUN cargo build -r; mv ./target/release/mango /mango; rm -rf ./target
+RUN --mount=type=cache,target=/usr/local/cargo/registry --mount=type=cache,target=/code/target \
+  cargo build -r; mv ./target/release/mango ./mango
 
-EXPOSE 8000
-CMD /mango
+FROM ubuntu
+RUN apt update; apt install -y libpq-dev
+COPY . .
+COPY --from=builder /code/mango /
 
+CMD /mango
+EXPOSE 8000
 LABEL org.opencontainers.image.source https://github.com/overlisted/mango