Multistage Docker build

docker/Dockerfile

@@ -1,7 +1,18 @@
-FROM alpine:latest
+FROM golang:1.16-alpine AS builder
 
-COPY restic /usr/bin
+WORKDIR /go/src/github.com/restic/restic
+
+# Caching dependencies
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN go run build.go
+
+FROM alpine:latest AS restic
 
 RUN apk add --update --no-cache ca-certificates fuse openssh-client tzdata
 
+COPY --from=builder /go/src/github.com/restic/restic/restic /usr/bin
+
 ENTRYPOINT ["/usr/bin/restic"]