Docker image executing golang executable: exec /usr/local/go/bin/go: exec format error

I understand that I need to specify the target platform of a go executable if it is supposed to run on another machine. I'm building a docker image on an apple machine with the M1 chip:

Dockerfile

FROM --platform=linux/amd64 golang:alpine AS build

WORKDIR /

ADD go.mod .
ADD go.sum .
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -o .

FROM --platform=linux/amd64 scratch

WORKDIR /app
COPY --from=build /foo /foo

CMD ["./foo"]

This appears to work because inspecting the container after build outputs

"Architecture": "amd64",
"Os": "linux"

But when I now start the image on a linux server using docker-compose, I get an error: exec /usr/local/go/bin/go: exec format error

docker-compose.yml

foo:
    environment:
      - PORT=${PORT}
    image: docker.io/name/foo
    platform: linux/amd64
    ports:
      - "8000:8000"
    restart: always

I'm pretty new to docker, so I guess I'm missing something quite obvious here.

First, I can confirm that you have successfully built an amd64 binary, so this isn't a go question.

If I run your image (on an amd64 linux system), I don't get the same error that you've reported. Given this docker-compose.yaml:

foo:
    environment:
      - PORT=${PORT}
    image: docker.io/chedched/foo
    platform: linux/amd64
    ports:
      - "8000:8000"
    restart: always

When running docker-compose up, I see:

ERROR: for images_foo_1  Cannot start service foo: failed to create shim task:
OCI runtime create failed: runc create failed: unable to start container
process: exec: "./foo": stat ./foo: no such file or directory: unknown

And this happens because you've set WORKDIR /app, which makes app the current working directory in your image, but you've installed your binary as /foo. You need to either:

• Change your CMD to reference the correct location:

  CMD ["/foo"]
  

  Or...

• Install the binary in /app:

  COPY --from=build /foo ./foo
  

With either of those changes, the image runs as expected.