use cargo-chef to cache build

Dockerfile

@@ -1,25 +1,34 @@
-FROM rust:1-alpine as builder
+FROM rust:1-alpine as chef
 
 ENV CARGO_REGISTRIES_CRATES_IO_PROTOCOL sparse
 
-RUN apk add --no-cache musl-dev
+RUN apk add --no-cache musl-dev curl
+
+# install cargo-binstall
+RUN curl -L --proto '=https' --tlsv1.2 -sSf https://raw.githubusercontent.com/cargo-bins/cargo-binstall/main/install-from-binstall-release.sh -o install-from-binstall-release.sh
+RUN sh install-from-binstall-release.sh
+
+# install cargo-chef
+RUN cargo binstall -y cargo-chef
 
 WORKDIR /home/rust/src
 
-COPY Cargo.toml /home/rust/src/
-COPY Cargo.lock /home/rust/src/
-RUN mkdir /home/rust/src/src && \
-    echo 'fn main() {}' > /home/rust/src/src/main.rs
+FROM chef AS planner
 
-RUN cargo fetch
+COPY . .
+
+RUN cargo chef prepare --recipe-path recipe.json
+
+FROM chef as builder
+COPY --from=planner /home/rust/src/recipe.json recipe.json
+
+# build & cache deps
+RUN cargo chef cook --release --recipe-path recipe.json
+
+# build app with cached deps
+COPY . .
 RUN cargo build --release
 
-RUN rm -f /home/rust/src/src/main.rs
-COPY src /home/rust/src/src
-RUN touch /home/rust/src/src/main.rs
-
-RUN cargo build -v --release
-
 FROM scratch
 
 COPY static /static