Added dockerfile

Dockerfile

@@ -0,0 +1,22 @@
+FROM --platform=${BUILDPLATFORM:-linux/amd64} golang:1.14-alpine as builder
+
+ARG TARGETPLATFORM
+ARG BUILDPLATFORM
+ARG TARGETOS
+ARG TARGETARCH
+
+WORKDIR /app/
+RUN apk update && apk add --no-cache git && adduser -D -g '' gopher && apk add -U --no-cache ca-certificates
+ADD go.mod go.sum ./
+RUN go mod download
+ADD . .
+RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags="-w -s" -o gopherss .
+
+FROM --platform=${TARGETPLATFORM:-linux/amd64} scratch
+WORKDIR /app/
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /etc/passwd /etc/passwd
+COPY --from=builder /app/gopherss /app/gopherss
+COPY ./web /app/web/
+USER gopher
+ENTRYPOINT ["/app/gopherss"]