Golang Dockerfile Failing - go

Question

I have a Golang web application that I am looking to run in Docker container. I am able to run it fine outside of the container, so I know it works, but when I build it from Dockerfile and run it, it gives me an error.
The Makefile looks like the following
GOCMD = go
GOBUILD = $(GOCMD) build
GOGET = $(GOCMD) get -v
GOCLEAN = $(GOCMD) clean
GOINSTALL = $(GOCMD) install
GOTEST = $(GOCMD) test
.PHONY: all
all: build
test:
$(GOTEST) -v -cover ./...
build:
$(GOGET); $(GOBUILD) -v -o engine
clean:
$(GOCLEAN) -n -i -x
rm -f $(GOPATH)/bin/engine
rm -rf bin/engine
install:
$(GOINSTALL)
And the Dockerfile looks like the following
FROM golang
ADD engine /go/bin/engine
EXPOSE 7777
ENTRYPOINT /go/bin/engine
I am building the image and running it using the following
docker build -t engine .
docker run -d --name engine -p 7777:7777 engine
and its giving me the following error
/go/bin/engine: 1: /go/bin/engine: Syntax error: "(" unexpected

Answer 1

When you build a binary, go build assumes that you are trying to build for your current computer, it chooses values for GOOS and GOARCH (described here) for you.
If you are not building on a linux machine then you will need to cross compile the binary for linux, as this is what the OS inside the docker container will be running. Explanation here
You need something like:
GOOS=linux
build:
$(GOGET); GOOS=$(GOOS) $(GOBUILD) -v -o engine