Improvements

Dockerfile

@@ -8,8 +8,17 @@ COPY src/ /usr/src/src/
 WORKDIR /usr/src
 
 RUN apk add --no-cache rustup build-base && \
-    rustup-init -qy --profile=minimal && \
+    rustup-init -qy --profile=minimal --default-toolchain=$RUST_VERSION && \
     source "$HOME/.cargo/env" && \
+    mkdir src && echo "fn main() {}" > src/main.rs && \
+    cargo fetch && \
+    cargo build --release --target=x86_64-unknown-linux-musl && \
+    rm src/main.rs
+
+COPY src/ /usr/src/src/
+
+RUN source "$HOME/.cargo/env" && \
+    touch src/main.rs && \
     cargo build --release --target=x86_64-unknown-linux-musl
 
 FROM alpine:$ALPINE_VERSION