fancylog provides stylized, non-blocking log output. It is designed to be fast, visually appealing, and highly configurable. It is used across many Golang projects here at NASK.

Features

• Extremely Fast: Optimized for performance with minimal overhead.
• Non-blocking: Designed to handle high-throughput logging without slowing down your application.
• Visual Clarity: Uses ANSI colors to distinguish between different log levels and components.
• Structured Logging: Supports logging maps and structured data for better machine readability.
• Specialized HTTP Logging: Includes a dedicated logger for HTTP requests with status code coloring.
• Middleware Support: Easy integration with Gin, gRPC, pgx, and standard net/http.
• Customizable: Configure names, timestamps, colors, and more.

Installation

go get github.com/n-ask/fancylog

Quick Start

Basic Logging

package main

import (
    "os"
    "github.com/n-ask/fancylog"
)

func main() {
    // Create a new logger with os.Stdout as output
    log := fancylog.New(os.Stdout)

    log.Info("Starting application...")
    log.Warn("This is a warning message.")
    log.Error("Something went wrong!")
    
    // Structured logging with maps
    log.InfoMap(map[string]any{
        "event": "user_login",
        "user_id": 123,
        "status": "success",
    })
}

HTTP Logging

package main

import (
    "os"
    "github.com/n-ask/fancylog"
)

func main() {
    // Create a specialized HTTP logger
    httpLog := fancylog.NewHttpLogger(os.Stdout)

    // Log an HTTP GET request with a 200 OK status
    httpLog.GetMethod(map[string]any{
        "uri": "/api/v1/users",
        "ip": "127.0.0.1",
    }, 200)

    // Log an error status
    httpLog.PostMethod(map[string]any{
        "uri": "/api/v1/login",
    }, 401)
}

Integration with Frameworks

Each integration lives in its own package under handlers/, so importing one pulls in that framework and nothing else:

Package	Provides	Pulls in
handlers/ginlog	GinLogger	Gin
handlers/httplog	LoggingHandler	httpsnoop
handlers/grpclog	Unary/Stream client and server interceptors	gRPC
handlers/pgxlog	FancyPGLogger for pgx query logging	pgx v5

These used to share a single handlers package. Go links at package granularity, so importing it for Gin middleware also compiled the gRPC and Postgres files — putting the whole pgx driver stack into binaries that never open a database connection.

Migrating from handlers: the symbols are unchanged, only their import path. handlers.GinLogger becomes ginlog.GinLogger, handlers.LoggingHandler becomes httplog.LoggingHandler, and the interceptors move to grpclog. The pgx logger additionally moved from pgx v4 to v5 — see handlers/pgxlog.

Gin Middleware

import (
    "github.com/gin-gonic/gin"
    "github.com/n-ask/fancylog"
    "github.com/n-ask/fancylog/handlers/ginlog"
)

r := gin.New()
log := fancylog.NewHttpLogger(os.Stdout)
r.Use(ginlog.GinLogger(log))

net/http Middleware

import (
    "net/http"
    "os"

    "github.com/n-ask/fancylog"
    "github.com/n-ask/fancylog/handlers/httplog"
)

log := fancylog.NewHttpLogger(os.Stdout)
srv := &http.Server{Handler: httplog.LoggingHandler(log, os.Stdout, mux)}

gRPC Interceptors

import (
    "google.golang.org/grpc"
    "github.com/n-ask/fancylog"
    "github.com/n-ask/fancylog/handlers/grpclog"
)

log := fancylog.New(os.Stdout)
s := grpc.NewServer(
    grpc.UnaryInterceptor(grpclog.UnaryServerInterceptor(log, fancylog.Info, myLogFunc, nil)),
)

pgx Query Logging

Targets pgx v5. v4 is not supported: GO-2026-5004 affects every v4 release with no fix available, and v4 depends on pgproto3/v2, whose GO-2026-4518 is likewise unfixed. v5 carries the fix and vendors its own pgproto3.

import (
    "github.com/jackc/pgx/v5/tracelog"
    "github.com/n-ask/fancylog"
    "github.com/n-ask/fancylog/handlers/pgxlog"
)

log := fancylog.New(os.Stdout)
cfg.Tracer = &tracelog.TraceLog{
    Logger:   pgxlog.NewFancyPGLogger(log),
    LogLevel: tracelog.LogLevelInfo,
}

Configuration

FancyLogger provides several methods to customize its behavior:

• WithColor() / WithoutColor(): Enable or disable ANSI colors.
• WithDebug() / WithoutDebug(): Show or hide debug and trace level logs.
• WithTimestamp() / WithoutTimestamp(): Enable or disable timestamps.
• Quiet() / NoQuiet(): Silence all output or resume logging.
• SetTimestampColor(color): Customize the color of the timestamp.
• NewWithName(name, output): Create a logger with a specific prefix name.