nginx-golang-mysql: add dev envs support (#274)

* Add Docker Desktop Development Environments config
* Use nginx image with read-only bind mount instead of building a
  custom image
* Upgrade Go dependencies

Co-authored-by: Guillaume Lours <guillaume@lours.me>
Signed-off-by: Milas Bowman <milas.bowman@docker.com>

nginx-golang-mysql/backend/Dockerfile

@@ -1,10 +1,41 @@
-FROM golang:1.13-alpine AS build
-WORKDIR /go/src/github.com/org/repo
+# syntax=docker/dockerfile:1.4
+FROM --platform=$BUILDPLATFORM golang:1.18-alpine AS builder
+
+WORKDIR /code
+
+ENV CGO_ENABLED 0
+ENV GOPATH /go
+ENV GOCACHE /go-build
+
+COPY go.mod go.sum ./
+RUN --mount=type=cache,target=/go/pkg/mod/cache \
+    go mod download
+
 COPY . .
 
-RUN go build -o server .
+RUN --mount=type=cache,target=/go/pkg/mod/cache \
+    --mount=type=cache,target=/go-build \
+    go build -o bin/backend main.go
 
-FROM alpine:3.12
-EXPOSE 8000
-COPY --from=build /go/src/github.com/org/repo/server /server
-CMD ["/server"]
+CMD ["/code/bin/backend"]
+
+FROM builder AS dev-envs
+
+RUN <<EOF
+apk update
+apk add git
+EOF
+
+RUN <<EOF
+addgroup -S docker
+adduser -S --shell /bin/bash --ingroup docker vscode
+EOF
+
+# install Docker tools (cli, buildx, compose)
+COPY --from=gloursdocker/docker / /
+
+CMD ["go", "run", "main.go"]
+
+FROM scratch
+COPY --from=builder /code/bin/backend /usr/local/bin/backend
+CMD ["/usr/local/bin/backend"]