use docker buildx to build docker images

Dockerfile

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+FROM golang:alpine AS builder
+RUN mkdir /godns
+ADD . /godns/
+WORKDIR /godns
+RUN go build -o godns cmd/godns/godns.go
+
+FROM alpine
+RUN apk add --update ca-certificates
+RUN mkdir /usr/local/godns
+COPY --from=builder /godns/godns /usr/local/godns
+RUN chmod +x /usr/local/godns/godns
+RUN rm -rf /var/cache/apk/*
+WORKDIR /usr/local/godns
+ENTRYPOINT ["./godns", "-c", "/usr/local/godns/config.json"]