build podsync inside docker

Dockerfile

@@ -1,10 +1,14 @@
-FROM alpine:3.10
+FROM golang:1.17.5-alpine3.15 AS builder
+WORKDIR /app
+COPY . /app/
+RUN go build -o podsync ./cmd/podsync
 
+FROM alpine:3.10
 WORKDIR /app/
 RUN wget -O /usr/bin/youtube-dl https://github.com/ytdl-org/youtube-dl/releases/latest/download/youtube-dl && \
     chmod +x /usr/bin/youtube-dl && \
     apk --no-cache add ca-certificates python ffmpeg tzdata
-COPY podsync /app/podsync
+COPY --from=builder /app/podsync /app/podsync
 
 ENTRYPOINT ["/app/podsync"]
 CMD ["--no-banner"]

Makefile

@@ -17,7 +17,6 @@ build:
 TAG ?= localhost/podsync
 .PHONY: docker
 docker:
-	GOOS=linux GOARCH=amd64 go build -o podsync ./cmd/podsync
 	docker build -t $(TAG) .
 	docker push $(TAG)