From 8488f68190c5aaaa3e67fcf1f0b058d21312e054 Mon Sep 17 00:00:00 2001
From: Nic Cope <nicc@rk0n.org>
Date: Sat, 21 Oct 2023 18:20:01 -0700
Subject: [PATCH] Use Go's native cross-compile support instead of emulation

Signed-off-by: Nic Cope <nicc@rk0n.org>
---
 Dockerfile | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/Dockerfile b/Dockerfile
index 5b4def2..6ae4d7d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,23 +2,24 @@
 
 # We use the latest Go 1.x version unless asked to use something else.
 ARG GO_VERSION=1
+ARG TARGETOS
+ARG TARGETARCH
 
 # Setup the base environment.
-FROM golang:${GO_VERSION} AS base
+FROM --platform=${BUILDPLATFORM} golang:${GO_VERSION} AS base
 
 WORKDIR /fn
 ENV CGO_ENABLED=0
 
 COPY go.mod go.sum ./
-RUN --mount=type=cache,target=/go/pkg/mod \
-    go mod download
+RUN --mount=type=cache,target=/go/pkg/mod go mod download
 
 # Build the Function.
 FROM base AS build
 RUN --mount=target=. \
     --mount=type=cache,target=/go/pkg/mod \
     --mount=type=cache,target=/root/.cache/go-build \
-    go build -o /function .
+    GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -o /function .
 
 # Produce the Function image.
 FROM gcr.io/distroless/base-debian11 AS image