From 2017d8b3660564208c16569ebc29109b08d8e4b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?M=C4=81ris=20Pop=C4=93ns?= <maris@popens.lv>
Date: Sun, 4 Oct 2026 19:36:39 +0300
Subject: [PATCH] perf: cross-compile arm64 instead of building under QEMU

---
 Dockerfile | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Dockerfile b/Dockerfile
index 7777e9e..c877099 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,10 +1,12 @@
 # Static CGO-free binary; distroless/static brings CA certs and nothing else.
-FROM golang:1.27-trixie AS builder
+# Cross-compile on the runner's own arch; building arm64 under QEMU took minutes.
+FROM --platform=$BUILDPLATFORM golang:1.27-trixie AS builder
+ARG TARGETOS TARGETARCH
 WORKDIR /src
 COPY go.mod go.sum ./
 RUN go mod download
 COPY . .
-RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /github-actions-runner-exporter .
+RUN CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH go build -trimpath -ldflags="-s -w" -o /github-actions-runner-exporter .
 
 FROM gcr.io/distroless/static-debian13:nonroot
 COPY --from=builder /github-actions-runner-exporter /github-actions-runner-exporter