Cross-compile for aarch64 instead of amd64

.drone.yml

@@ -2,7 +2,7 @@
 kind: pipeline
 name: default
 steps:
-- name: docker
+- name: docker_aarch64
   image: plugins/docker
   settings:
     registry: atdr-writer.meo.ws
@@ -14,5 +14,7 @@ steps:
     dockerfile: Containerfile
     purge: true
     auto_tag: false
+    build_args:
+    - GOARCH=aarch64
     tags:
-    - latest
+    - ${DRONE_BRANCH}-aarch64

Containerfile

@@ -12,7 +12,9 @@ WORKDIR /go/src/github.com/dutchcoders/transfer.sh
 ENV GO111MODULE=on
 
 # build & install server
-RUN go get ./... && CGO_ENABLED=0 go build -ldflags -a -tags netgo -ldflags '-w -extldflags "-static"' -o /go/bin/transfersh github.com/dutchcoders/transfer.sh
+ARG GOOS=linux
+ARG GOARCH=amd64
+RUN go get ./... && CGO_ENABLED=0 GOOS=${GOOS} GOARCH=${GOARCH} go build -ldflags -a -tags netgo -ldflags '-w -extldflags "-static"' -o /go/bin/transfersh github.com/dutchcoders/transfer.sh
 
 FROM scratch AS final
 LABEL maintainer="Andrea Spacca <andrea.spacca@gmail.com>"