feat: add cache layer in docker building

Author: BoynChan

Dockerfile

@@ -1,7 +1,17 @@
 FROM rust:1.65 as builder
+
+RUN cargo new --bin app
 WORKDIR /app
 COPY Cargo.toml Cargo.toml
+# Dry running build command to make Docker cache layer
+RUN cargo build --release
+RUN rm src/*.rs
+
 COPY src src
 RUN cargo build --release
+
+# Use slim image to place build result
+FROM debian:stable-slim
+COPY --from=builder ./app/target/release/chatgpt-proxy-server .
 EXPOSE 3000
-CMD ["./target/release/chatgpt-proxy-server"]
+CMD ["./chatgpt-proxy-server"]