Optimize Docker build with bind mounts

This commit further optimize the Docker builds on top of PR #92 with:

1. Add .dockerignore file to exclude non-source code files [1].

2. Use Alpine image variant for build stage to reduce download size.
   golang:1.23.7-alpine is 200 MB smaller than golang:1.23.7 [2][3].

3. Replace COPY instruction with RUN --mount=type=bind. Bind mounts do
   not add unnecessary layers to the cache [4][5].

[1]: https://docs.docker.com/build-cloud/optimization/#dockerignore-files
[2]: https://hub.docker.com/layers/library/golang/1.23.7-alpine/images/sha256-333d4ba78773b3a3ae9cf2cff8962df56effc5c9481faa355f211abf2baf175c
[3]: https://hub.docker.com/layers/library/golang/1.23.7/images/sha256-2087a99c3235972660b3d35c1564d9d1a3f639dcace9c790acbabc7e938d1570
[4]: https://docs.docker.com/build/building/best-practices/#add-or-copy
[5]: https://docs.docker.com/build/cache/optimize/#use-bind-mounts

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

Author: Juneezee

.dockerignore

@@ -0,0 +1,11 @@
+.github
+.vscode
+script
+third-party
+.dockerignore
+.gitignore
+**/*.yml
+**/*.yaml
+**/*.md
+**/*_test.go
+LICENSE

Dockerfile

@@ -1,27 +1,31 @@
+FROM golang:1.23.7-alpine AS build
 ARG VERSION="dev"
 
-FROM golang:1.23.7 AS build
-# allow this step access to build arg
-ARG VERSION
 # Set the working directory
 WORKDIR /build
 
-RUN go env -w GOMODCACHE=/root/.cache/go-build
+# Install git
+RUN --mount=type=cache,target=/var/cache/apk \
+    apk add git
 
 # Install dependencies
-COPY go.mod go.sum ./
-RUN --mount=type=cache,target=/root/.cache/go-build go mod download
+RUN --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=bind,source=go.mod,target=go.mod \
+    --mount=type=bind,source=go.sum,target=go.sum \
+    go mod download
 
-COPY . ./
 # Build the server
-RUN --mount=type=cache,target=/root/.cache/go-build CGO_ENABLED=0 go build -ldflags="-s -w -X main.version=${VERSION} -X main.commit=$(git rev-parse HEAD) -X main.date=$(date -u +%Y-%m-%dT%H:%M:%SZ)" \
-    -o github-mcp-server cmd/github-mcp-server/main.go
+RUN --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    --mount=type=bind,target=. \
+    CGO_ENABLED=0 go build -ldflags="-s -w -X main.version=${VERSION} -X main.commit=$(git rev-parse HEAD) -X main.date=$(date -u +%Y-%m-%dT%H:%M:%SZ)" \
+    -o /bin/github-mcp-server cmd/github-mcp-server/main.go
 
 # Make a stage to run the app
 FROM gcr.io/distroless/base-debian12
 # Set the working directory
 WORKDIR /server
 # Copy the binary from the build stage
-COPY --from=build /build/github-mcp-server .
+COPY --from=build /bin/github-mcp-server .
 # Command to run the server
 CMD ["./github-mcp-server", "stdio"]