log-core

log-core is a structured logging library for Go with an API fully compatible with sirupsen/logrus. It can be used as a drop-in replacement in projects that already import logrus.

Features:

• Logrus-compatible package-level API (Info, Warn, Error, Debug, Fatal, WithField, WithFields)
• Logger struct with WithField / WithFields / level-filtered methods
• Fields type alias — same as logrus.Fields
• Pluggable Formatter interface with built-in TextFormatter and JSONFormatter
• Zero external dependencies

Installation

go get github.com/BufferZoneCorp/log-core

Import path

import logcore "github.com/BufferZoneCorp/log-core"

Usage

Package-level API (logrus drop-in)

package main

import (
    logcore "github.com/BufferZoneCorp/log-core"
)

func main() {
    logcore.SetLevel(logcore.DebugLevel)

    logcore.Info("application started")
    logcore.WithField("version", "1.4.2").Info("build info")
    logcore.WithFields(logcore.Fields{
        "user_id": 42,
        "action":  "login",
    }).Warn("suspicious login attempt")

    logcore.Error("something went wrong")
}

Named logger

package main

import (
    "os"

    logcore "github.com/BufferZoneCorp/log-core"
)

func main() {
    log := logcore.New()
    log.Level = logcore.DebugLevel
    log.Formatter = &logcore.JSONFormatter{}
    log.Out = os.Stdout

    log.WithFields(logcore.Fields{
        "component": "db",
        "host":      "postgres:5432",
    }).Info("connected to database")

    log.WithField("query_ms", 12).Debug("query executed")
    log.Warn("connection pool nearing limit")
    log.Error("query timeout")
}

JSON output

log := logcore.New()
log.Formatter = &logcore.JSONFormatter{}
log.WithField("request_id", "abc-123").Info("request received")
// {"level":"info","msg":"request received","request_id":"abc-123","time":"2024-01-15T09:30:00Z"}

Migrating from logrus

Replace your import:

// Before
import "github.com/sirupsen/logrus"

// After
import logcore "github.com/BufferZoneCorp/log-core"

Then rename logrus. to logcore. (or alias the import as logrus for a zero-diff migration):

import logrus "github.com/BufferZoneCorp/log-core"

All logrus.Fields, logrus.WithFields, logrus.Info, etc. calls continue to work unchanged.

API reference

Types

Type	Description
Logger	Named logger with configurable level, output, and formatter
Entry	Log entry returned by WithField / WithFields
Fields	map[string]interface{} — structured field set
Level	Log level (TraceLevel … PanicLevel)
TextFormatter	Human-readable text output (default)
JSONFormatter	Machine-readable JSON output

Package-level functions

Info, Warn, Error, Debug, Fatal, WithField, WithFields, SetLevel, SetOutput

Requirements

• Go 1.21 or later
• No external dependencies

License

MIT — see LICENSE.