How to Fix the \"Cannot Find Package\" Error When Building Docker Images with Go Applications?

Troubleshooting "Cannot Find Package" Error When Building Docker with Go App

When building a Docker image with a Go application, you may encounter an error stating "cannot find package." The root cause of this error often lies in the Dockerfile setup.

Problem Definition

The Dockerfile specified in the original question attempts to build a Go application and run the resulting executable from /go/bin/myapp. However, this approach results in an error because the Dockerfile does not explicitly install the Go application dependencies or compile the application.

Solution

To resolve this issue, one needs to modify the Dockerfile to include the following steps:

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

1. Copy project files: Use ADD . /go/src/myapp to copy all project files to /go/src/myapp.
2. Set working directory: Set the working directory to /go/src/myapp using WORKDIR /go/src/myapp.
3. Install dependencies: Install the application dependencies using go get myapp.
4. Install/build the binary: Run go install to compile the Go application.
5. Set entry point: Specify the entry point as /go/bin/myapp to run the compiled executable.

Debugging Docker Build Process

To better understand the Docker build process, one can use the following commands:

• docker exec: Execute a command inside an existing container.
• docker run --rm -it [image hash/name] /bin/sh: Enter an interactive shell inside the image for further exploration.

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