utils

Mjolnir

Mjolnir is an opinionated wrapper around go-chi/chi that provides enhanced middleware and utilities for building HTTP services in Go. It adds structured logging, request ID tracking, and standardized error handling out of the box.

Features

• Request Logging: Built-in zerolog-based structured logging middleware that captures:

  • Request ID
  • HTTP method
  • Path
  • Remote address
  • Status code
  • Request latency

• Request ID Tracking: Automatic request ID generation and propagation

  • Generates UUID-based request IDs
  • Respects existing X-Request-ID headers
  • Adds request ID to response headers
  • Available throughout the request context

• Standardized Error Handling: Comprehensive error management system

  • Consistent JSON error responses
  • Automatic internal error logging
  • Panic recovery
  • Helper functions for common HTTP status codes
  • Context-based error propagation

Installation

go get github.com/dfryer1193/mjolnir

Requirements

• Go 1.24 or later
• github.com/go-chi/chi/v5
• github.com/rs/zerolog
• github.com/google/uuid

Usage

Basic Example

package main

import (
    "github.com/dfryer1193/mjolnir/router"
    "github.com/rs/zerolog/log"
    "net/http"
)

func main() {
    r := router.New()

    r.Get("/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("Hello World!"))
    })

    r.Get("/panic", func(w http.ResponseWriter, r *http.Request) {
        panic("This is a panic")
    })

    log.Info().Msg("Server starting on :8080")
    http.ListenAndServe(":8080", r)
}

Error Response Format

All errors are returned as JSON with the following structure:

{
    "error": "Error message",
    "code": 400
}

Error Handling Behavior

The error handler distinguishes between internal (500-level) and other errors:

• Internal Server Errors (500+):
  • Logs the full error details including stack trace to the server logs
  • Returns a generic "Internal Server Error" message to the client
  • Includes request ID in logs for correlation
  • Always returns status code 500

Example internal error response:

{
    "error": "Internal Server Error",
    "code": 500
}

• Other Errors (4xx):
  • Returns the actual error message to the client
  • Includes the specific status code
  • Does not log detailed error information

Example client error response:

{
    "error": "Resource not found",
    "code": 404
}

This approach ensures that sensitive internal error details are never exposed to clients while still providing meaningful error messages for client-side issues.