Dockerfile

FROM crystallang/crystal:1.0.0-alpine
COPY . /src
WORKDIR /src
RUN shards build --release --static

FROM golang:alpine
RUN go get -u github.com/vishen/go-chromecast

FROM scratch
COPY --from=0 /src/bin/castblock /usr/bin/castblock
COPY --from=1 /go/bin/go-chromecast /usr/bin/go-chromecast
ENV PATH=/usr/bin
ENTRYPOINT ["/usr/bin/castblock"]

gistfile1.txt

$ docker run --rm --init --network=host test
2021-04-23T18:07:43.715959Z   INFO - castblock.chromecast: Found go-chromecast at /usr/bin/go-chromecast.
2021-04-23T18:07:43.716016Z   INFO - castblock.chromecast: Starting the go-chromecast server.
Unhandled exception in spawn: Error executing process: '/usr/bin/go-chromecast': No such file or directory (File::NotFoundError)
  from usr/share/crystal/src/crystal/system/unix/process.cr:225:34 in 'raise_exception_from_errno'
  from usr/share/crystal/src/array.cr:2060:14 in 'initialize'
  from usr/share/crystal/src/process.cr:221:3 in 'start_server'
  from src/src/chromecast.cr:18:5 in '->'
  from usr/share/crystal/src/primitives.cr:255:3 in 'run'
  from ??