Building a Docker Container for Your Golang Web Application Made Easy

Learn how to create a Dockerfile for your Golang web application, ensuring all directory structures are respected and dependencies are managed effectively.
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This video is based on the question https://stackoverflow.com/q/75973805/ asked by the user 'Radin Khosraviani' ( https://stackoverflow.com/u/15022214/ ) and on the answer https://stackoverflow.com/a/75976939/ provided by the user 'Ashutosh Singh' ( https://stackoverflow.com/u/14669005/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Building a Docker Container for Your Golang Web Application Made Easy

Creating a Docker container for your Golang web application can sometimes feel challenging, especially when dealing with specific directory structures. In this post, we’ll take a closer look at a common problem faced by developers—getting a Dockerfile configured correctly to build and run a web app in Go. We’ll walk through the adjustments necessary in your Dockerfile to overcome these obstacles, making it easier to run your application seamlessly on multiple devices.

Understanding the Problem

You have a Golang web application with the following project structure:

[[See Video to Reveal this Text or Code Snippet]]

Your initial Dockerfile ran into issues stating that there were "no Go files in /build" since the main Go files were located in /cmd/web/.

The Original Dockerfile

[[See Video to Reveal this Text or Code Snippet]]

The issue arose when you attempted to run the build command that targeted the cmd/web path, as the necessary module files (go.mod and go.sum) were not getting copied over correctly leading to further compilation errors.

The Solution

To effectively build your web application, we must modify the Dockerfile to ensure that it properly copies and downloads the required Go module files. Below is the optimized Dockerfile that addresses the previously mentioned issues:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of Changes

Setup the Working Directory: The WORKDIR /app sets the current working directory for any RUN, CMD, ENTRYPOINT, or COPY instructions that follow.

Copy Go Module Files:

COPY go.mod .

COPY go.sum .
These commands ensure that the go module files are available during the Docker build process.

Download Dependencies:

RUN go mod download fetches all dependencies specified in your module files, preparing your environment for a successful build.

Copy the Application Code:

COPY . . copies all of the source code into the Docker container, including your Go files.

Build Application:

RUN go build -o /myapp ./cmd/web specifically builds the application located in the cmd/web directory.

Prepare the Runtime Environment:

The COPY command in the second stage moves the built application into a light-weight Alpine image, which is then set to run on port 8080.

Conclusion

With these tailored changes, you should now be able to build and run your Golang web application in a Docker container without any hassle. This Dockerfile respects your project structure and ensures that all necessary components are included during the build phase. Feel free to experiment further with your application, and enjoy the efficiency that Docker brings to your development process!

If you have any questions, leave a comment below!

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