new.Dockerfile

FROM --platform=$BUILDPLATFORM golang:1.17-alpine AS build
WORKDIR /go/src/github.com/docker/cli
ENV GO111MODULE=auto
ARG TARGETOS TARGETARCH
RUN --mount=target=. \
    --mount=type=cache,target=/root/.cache/go-build \
    --mount=type=cache,target=/go/pkg \
    GOOS=$TARGETOS GOARCH=$TARGETARCH go build -o /out/docker ./cmd/docker

FROM alpine
COPY --from=build /out/docker /bin

old.Dockerfile

FROM golang:1.17-alpine AS build
WORKDIR /go/src/github.com/docker/cli
COPY . .
ENV GO111MODULE=auto
RUN go build -o /out/docker ./cmd/docker

FROM alpine
COPY --from=build /out/docker /bin