使用Go应用构建Docker：找不到软件包

Question

I have my Dockerfile in the root of directory with src/myapp folder, myapp contains myapp.go with main package.

Dockerfile looks like following:

FROM golang:1.9.2

ADD . /
RUN go build myapp;

ENTRYPOINT ["/go/bin/myapp"]

I get following error:

can't load package: package myapp: cannot find package "myapp" in any of:
    /usr/local/go/src/myapp (from $GOROOT)
    /go/src/myapp (from $GOPATH)

What am I doing wrong? Can I log ls command after docker has done ADD?

Answer 1

You are copying all the files to Image root directory, Didn't installed any dependencies, Trying to Build it and then run the binary from /go/bin/app. The binary doesn't exists in that directory and it's generating errors.

I would recommend using a Dockerfile like this,

FROM golang:1.9.2 
ADD . /go/src/myapp
WORKDIR /go/src/myapp
RUN go get myapp
RUN go install
ENTRYPOINT ["/go/bin/myapp"]

This'll do the following.

1. Copy project files to /go/src/myapp.
2. Set Working directory to /go/src/myapp.
3. Install dependencies, I used go get but replace it with which ever dependency management tool you are using.
4. Install/build the binary.
5. Set entry point.

You can run ls or any other command using docker exec.

Example:

docker exec <image name/hash> ls

You can also enter the shell in the generated image to understand it well using

docker run --rm -it <image hash/name> /bin/sh