date-wizard/.github/prompts/7-create-docker-microservice.prompt.md

I want to add backend functionality to send the survey responses as an email upon submission using Option 1 (a minimalist Go/Golang microservice).

Please complete the following tasks:

1. Go Microservice (main.go):

   • Create a lightweight HTTP server using standard Go library packages (net/http, net/smtp, encoding/json).
   • Create an endpoint (e.g., POST /api/submit) to accept JSON payload survey data from the front end.
   • Configure SMTP credentials and server settings via environment variables (e.g., SMTP_HOST, SMTP_PORT, SMTP_USER, SMTP_PASS, TO_EMAIL) via an .env file
   • Format the incoming JSON survey data into a clean, readable text body and dispatch the email upon request.
   • Handle CORS preflight (OPTIONS) and headers so the HTML/JS front end can POST to it smoothly.

2. Dockerization (Dockerfile):

   • Provide a multi-stage Dockerfile (e.g., compile with golang:alpine, copy to scratch or alpine) to ensure the resulting container image is ultra-lightweight (<20MB).

3. Front-End Integration:

   • Show how to update the existing JavaScript submission handler (using fetch()) to send the survey data as JSON to the new Go backend endpoint.

Please keep the code minimalist, robust, and well-commented.

when everything works, please create a simple docker-compose file that builds the project and runs the container. include traefik labels for reverse proxy routing.