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build: Cache during Docker build for speed #29

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Merged
Peeja merged 1 commit into from
Apr 21, 2026
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build: Cache during Docker build for speed #29

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11 changes: 8 additions & 3 deletions Dockerfile
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Original file line number Diff line number Diff line change
Expand Up @@ -4,17 +4,22 @@ ARG TARGETARCH
ARG TARGETOS=linux
WORKDIR /go/src/sprue
COPY go.mod go.sum* ./
RUN go mod download || true
RUN --mount=type=cache,target=/go/pkg/mod \
go mod download || true
COPY . .

# Production build - stripped binary
FROM build AS build-prod
RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} \
RUN --mount=type=cache,target=/go/pkg/mod \
--mount=type=cache,target=/root/.cache/go-build \
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@alanshaw alanshaw Apr 21, 2026

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Can you explain what's going on here? Is this caching twice? Why is that?

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@Peeja Peeja Apr 21, 2026

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It's caching two directories: the dependency cache and the build cache. This means it doesn't have to re-download modules every build, and it…builds faster? I'm not sure how the build cache works, but apparently it can cache bits of the build.

CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} \
go build -ldflags="-s -w" -o /sprue ./cmd/main.go

# Development build - debug-friendly binary
FROM build AS build-dev
RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} \
RUN --mount=type=cache,target=/go/pkg/mod \
--mount=type=cache,target=/root/.cache/go-build \
CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} \
go build -gcflags="all=-N -l" -o /sprue ./cmd/main.go
RUN GOARCH=${TARGETARCH} go install github.com/go-delve/delve/cmd/dlv@latest && \
cp /go/bin/linux_${TARGETARCH}/dlv /go/bin/dlv 2>/dev/null || cp /go/bin/dlv /go/bin/dlv 2>/dev/null || true
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