Dockerfile for use with raspberry 64bit

[skara]

Tried to get docui running on raspberry pi 64bit
To build it directly via docker you may use following:

# build docui
FROM golang:1.16.0 AS build-docui
ENV GOOS linux
ENV GOARCH=arm
ENV GOARM=7
ENV CGO_ENABLED 0
COPY . ./src/github.com/skanehira/docui
WORKDIR /go/src/github.com/skanehira/docui
RUN go build

# copy artifact from the build stage
FROM busybox:1.33
ENV TERM "xterm-256color"
COPY --from=build-docui /go/src/github.com/skanehira/docui/docui /usr/local/bin/docui

ENTRYPOINT ["docui"]```

Maybe someone could do a multiarch Dockerfile