Docker Configuration

This section outlines the Docker configuration used within the development environment for benhall/golang-demo.

Building the Docker Image

The Dockerfile leverages a two-stage build process to optimize the resulting image size:

• Stage 1: Builder Stage

  • This stage utilizes the golang:1.21-alpine base image.
  • The working directory is set to /app.
  • The go.mod and go.sum files are copied into the container.
  • Dependencies are downloaded and the go.sum file is updated.
  • The entire application code is copied to the container.
  • The application is built using go build -o myapp.

  # First stage: build the application
  FROM golang:1.21-alpine AS builder
  
  # Set the working directory
  WORKDIR /app
  
  # Copy go.mod
  COPY go.mod go.sum ./
  
  # Download dependencies and generate go.sum
  RUN go mod download && go mod tidy
  
  # Copy the rest of the application code
  COPY . .
  
  # Build the application
  RUN go build -o myapp
  

• Stage 2: Runtime Stage

  • This stage utilizes the alpine:latest base image.
  • The working directory is set to /root/.
  • The built application binary (myapp) is copied from the builder stage.
  • The container exposes port 8080 to the outside world.
  • The CMD instruction specifies the command to run the executable: ./myapp.

  # Second stage: create the runtime image
  FROM alpine:latest
  
  # Set the working directory
  WORKDIR /root/
  
  # Copy the built application from the builder stage
  COPY --from=builder /app/myapp .
  
  # Expose port 8080 to the outside world
  EXPOSE 8080
  
  # Command to run the executable
  CMD ["./myapp"]
  

To build the Docker image, navigate to the project root directory and run the following command:

docker build -t golang-demo .

Running the Docker Image

Once the image is built, it can be run with the following command:

docker run --name=golang-http-demo -p 8082:8080 -itd golang-demo

This command:

• Creates a container named golang-http-demo.
• Maps port 8082 on the host machine to port 8080 inside the container.
• Runs the container in detached mode (-d) and starts an interactive terminal (-it).

Testing the Application

To test the application running in the container, you can use curl:

curl localhost:8082

This command will send a request to the localhost:8082 endpoint and display the response, which should be “Hello, World!”.