Download gomplate during building phase

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

Dockerfile

@@ -7,11 +7,16 @@ RUN apk add --no-cache --update alpine-sdk
 ARG TARGETOS
 ARG TARGETARCH
 ARG TARGETVARIANT=""
+ARG GOMPLATE_VERSION=v3.9.0
 
 ENV GOOS=${TARGETOS} GOARCH=${TARGETARCH} GOARM=${TARGETVARIANT}
 
 ARG GOPROXY
 
+RUN wget -O /usr/local/bin/gomplate \
+  "https://github.com/hairyhenderson/gomplate/releases/download/${GOMPLATE_VERSION}/gomplate_${GOOS:-linux}-${GOARCH:-amd64}${GOARM}" \
+  && chmod +x /usr/local/bin/gomplate
+
 COPY go.mod go.sum ./
 COPY api/v2/go.mod api/v2/go.sum ./api/v2/
 RUN go mod download
@@ -27,14 +32,8 @@ FROM alpine:3.13.1
 # experience when this doesn't work out of the box.
 #
 # OpenSSL is required so wget can query HTTPS endpoints for health checking.
-ARG TARGETARCH
-ARG TARGETVARIANT=""
-ARG GOMPLATE_VERSION=v3.9.0
 
 RUN apk add --no-cache --update ca-certificates openssl
-RUN wget -O /usr/local/bin/gomplate \
-  "https://github.com/hairyhenderson/gomplate/releases/download/${GOMPLATE_VERSION}/gomplate_linux-${TARGETARCH:-amd64}${TARGETVARIANT}" \
-  && chmod +x /usr/local/bin/gomplate
 
 RUN mkdir -p /var/dex
 RUN chown -R 1001:1001 /var/dex
@@ -47,6 +46,7 @@ RUN chown -R 1001:1001 /etc/dex
 COPY --from=builder /usr/local/src/dex/go.mod /usr/local/src/dex/go.sum /usr/local/src/dex/
 COPY --from=builder /usr/local/src/dex/api/v2/go.mod /usr/local/src/dex/api/v2/go.sum /usr/local/src/dex/api/v2/
 
+COPY --from=builder /usr/local/bin/gomplate /usr/local/bin/gomplate
 COPY --from=builder /go/bin/dex /usr/local/bin/dex
 
 USER 1001:1001