Environment Variables

Overview

go_logs supports configuration via environment variables, making it easy to adjust logging behavior across different environments without code changes. Environment variables are automatically loaded when using the v2 legacy API or can be manually loaded for v3 loggers.

Log Level

LOG_LEVEL

Sets the minimum log level threshold. Only messages at or above this level will be logged. Type: String (case-insensitive) Valid Values:

trace - Extremely detailed, high-volume logging (Level 10)
debug - Detailed diagnostic information (Level 20)
info - General informational messages (Level 30, default)
warn or warning - Warning messages (Level 40)
error - Error events (Level 50)
fatal - Critical errors that terminate the app (Level 60)
silent, none, or disable - Disable all logging (Level 0)

Default: If not set, the legacy notification system is used (v2 backward compatibility) Example:

export LOG_LEVEL=info

Usage:

// v2 API (automatic)
go_logs.Init()
go_logs.InfoLog("This will be logged")
go_logs.DebugLog("This will be filtered out")

// v3 API (via config)
logger, _ := go_logs.New(
    go_logs.WithLevel(go_logs.ParseLevel(os.Getenv("LOG_LEVEL"))),
)

Output Format

LOG_FORMAT

Sets the output format for log entries. Type: String (case-insensitive) Valid Values:

text - Human-readable text with colors (default)
json - Structured JSON for log aggregation

Default: text Example:

# Development
export LOG_FORMAT=text

# Production
export LOG_FORMAT=json

Output Examples: Text format:

[2026/03/03 15:30:00] INFO connection established host=db.example.com port=5432

JSON format:

{"timestamp":"2026-03-03T15:30:00Z","level":"INFO","message":"connection established","fields":{"host":"db.example.com","port":5432}}

File Logging

SAVE_LOG_FILE

Enables or disables logging to a file. Type: Boolean (0 or 1) Default: 0 (disabled) Example:

export SAVE_LOG_FILE=1

LOG_FILE_NAME

Sets the name of the log file. Type: String Default: log.txt Example:

export LOG_FILE_NAME=app.log

LOG_FILE_PATH

Sets the directory path for log files. Type: String (directory path) Default: Current directory (.) Example:

export LOG_FILE_PATH=/var/log/myapp

Complete File Logging Example:

export SAVE_LOG_FILE=1
export LOG_FILE_NAME=application.log
export LOG_FILE_PATH=/var/log
# Creates /var/log/application.log

File Rotation (v3)

LOG_MAX_SIZE

Maximum log file size in megabytes before rotation occurs. Type: Integer (MB) Default: 100 MB Example:

export LOG_MAX_SIZE=50  # Rotate at 50 MB

LOG_MAX_BACKUPS

Maximum number of backup files to keep after rotation. Type: Integer Default: 5 Example:

export LOG_MAX_BACKUPS=10  # Keep last 10 rotated files

Rotation Example:

export LOG_MAX_SIZE=100
export LOG_MAX_BACKUPS=5

# Creates:
# app.log       (current)
# app.log.1     (most recent backup)
# app.log.2
# app.log.3
# app.log.4
# app.log.5     (oldest backup, deleted on next rotation)

Usage in Code:

// Load from environment
maxSizeMB, _ := strconv.Atoi(os.Getenv("LOG_MAX_SIZE"))
maxBackups, _ := strconv.Atoi(os.Getenv("LOG_MAX_BACKUPS"))

logger, _ := go_logs.New(
    go_logs.WithRotatingFile(
        os.Getenv("LOG_FILE_PATH")+"/"+os.Getenv("LOG_FILE_NAME"),
        maxSizeMB,
        maxBackups,
    ),
)

Slack Notifications

SLACK_TOKEN

Slack bot token for sending notifications. Type: String (OAuth token) Format: xoxb-... Example:

export SLACK_TOKEN=xoxb-123456789-abcdefghijk

SLACK_CHANNEL_ID

Slack channel ID where notifications will be sent. Type: String (Channel ID) Format: C... or G... Example:

export SLACK_CHANNEL_ID=C0123456789

NOTIFICATIONS_SLACK_ENABLED

Enables or disables Slack notifications. Type: Boolean (0 or 1) Default: 0 (disabled) Example:

export NOTIFICATIONS_SLACK_ENABLED=1
export SLACK_TOKEN=xoxb-your-token
export SLACK_CHANNEL_ID=C0123456789

Legacy Notification Levels (v2)

These variables control which log levels trigger Slack notifications in the v2 API. If any are set, they take precedence over LOG_LEVEL for backward compatibility.

NOTIFICATION_FATAL_LOG

Send fatal logs to Slack. Type: Boolean (0 or 1) Default: 0 Example:

export NOTIFICATION_FATAL_LOG=1

NOTIFICATION_ERROR_LOG

Send error logs to Slack. Type: Boolean (0 or 1) Default: 0 Example:

export NOTIFICATION_ERROR_LOG=1

NOTIFICATION_WARNING_LOG

Send warning logs to Slack. Type: Boolean (0 or 1) Default: 0 Example:

export NOTIFICATION_WARNING_LOG=1

NOTIFICATION_INFO_LOG

Send info logs to Slack. Type: Boolean (0 or 1) Default: 0 Example:

export NOTIFICATION_INFO_LOG=1

NOTIFICATION_SUCCESS_LOG

Send success logs to Slack. Type: Boolean (0 or 1) Default: 0 Example:

export NOTIFICATION_SUCCESS_LOG=1

Configuration Priority

go_logs uses the following priority for configuration (highest to lowest):

Programmatic configuration (v3 New() options)
Legacy notification variables (NOTIFICATION_*_LOG)
LOG_LEVEL environment variable
Default values (InfoLevel, text format, etc.)

Example:

# If both are set, NOTIFICATION_ERROR_LOG takes precedence
export LOG_LEVEL=info
export NOTIFICATION_ERROR_LOG=1

Environment Configuration Examples

Development Environment

# .env.development
LOG_LEVEL=debug
LOG_FORMAT=text
SAVE_LOG_FILE=0  # Console only

Staging Environment

# .env.staging
LOG_LEVEL=info
LOG_FORMAT=json
SAVE_LOG_FILE=1
LOG_FILE_NAME=staging.log
LOG_FILE_PATH=/var/log/myapp
LOG_MAX_SIZE=100
LOG_MAX_BACKUPS=5

# Slack notifications for errors
NOTIFICATIONS_SLACK_ENABLED=1
SLACK_TOKEN=xoxb-staging-token
SLACK_CHANNEL_ID=C_STAGING

Production Environment

# .env.production
LOG_LEVEL=warn  # Only warnings and errors
LOG_FORMAT=json
SAVE_LOG_FILE=1
LOG_FILE_NAME=production.log
LOG_FILE_PATH=/var/log/myapp
LOG_MAX_SIZE=200  # Larger files
LOG_MAX_BACKUPS=10  # Keep more backups

# Slack notifications for errors and fatal
NOTIFICATIONS_SLACK_ENABLED=1
SLACK_TOKEN=xoxb-production-token
SLACK_CHANNEL_ID=C_ALERTS
NOTIFICATION_FATAL_LOG=1
NOTIFICATION_ERROR_LOG=1

Docker Configuration

# Dockerfile
FROM golang:1.21

# Set default log configuration
ENV LOG_LEVEL=info \
    LOG_FORMAT=json \
    SAVE_LOG_FILE=0

COPY . /app
WORKDIR /app

RUN go build -o myapp

CMD ["./myapp"]

# docker-compose.yml
version: '3.8'
services:
  app:
    build: .
    environment:
      - LOG_LEVEL=debug
      - LOG_FORMAT=text
      - SAVE_LOG_FILE=1
      - LOG_FILE_PATH=/var/log
      - SLACK_TOKEN=${SLACK_TOKEN}
      - SLACK_CHANNEL_ID=${SLACK_CHANNEL_ID}
    volumes:
      - ./logs:/var/log

Kubernetes Configuration

# deployment.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-logging-config
data:
  LOG_LEVEL: "info"
  LOG_FORMAT: "json"
  LOG_MAX_SIZE: "100"
  LOG_MAX_BACKUPS: "5"
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  template:
    spec:
      containers:
      - name: app
        image: myapp:latest
        envFrom:
        - configMapRef:
            name: app-logging-config
        env:
        - name: SLACK_TOKEN
          valueFrom:
            secretKeyRef:
              name: slack-credentials
              key: token
        - name: SLACK_CHANNEL_ID
          valueFrom:
            secretKeyRef:
              name: slack-credentials
              key: channel

Loading Environment Variables

v2 API (Automatic)

The v2 API automatically loads environment variables when Init() is called:

import "github.com/drossan/go_logs"

func main() {
    go_logs.Init()  // Loads all environment variables
    defer go_logs.Close()
    
    go_logs.InfoLog("Application started")
}

v3 API (Manual)

The v3 API requires explicit configuration, but you can load from environment:

import (
    "os"
    "strconv"
    "github.com/drossan/go_logs"
)

func main() {
    // Parse environment variables
    level := go_logs.ParseLevel(os.Getenv("LOG_LEVEL"))
    
    maxSize, _ := strconv.Atoi(os.Getenv("LOG_MAX_SIZE"))
    if maxSize == 0 {
        maxSize = 100 // default
    }
    
    maxBackups, _ := strconv.Atoi(os.Getenv("LOG_MAX_BACKUPS"))
    if maxBackups == 0 {
        maxBackups = 5 // default
    }
    
    // Create logger from environment
    logger, err := go_logs.New(
        go_logs.WithLevel(level),
        go_logs.WithRotatingFile(
            os.Getenv("LOG_FILE_PATH")+"/"+os.Getenv("LOG_FILE_NAME"),
            maxSize,
            maxBackups,
        ),
    )
    if err != nil {
        panic(err)
    }
    defer logger.Sync()
    
    logger.Info("Application started")
}

Next Steps

Configuration Options - Programmatic configuration
Output Destinations - File rotation and multiple outputs
Quick Start - Basic usage examples

Get Started

Core Concepts

Configuration

Advanced Features

Optional Modules

Testing

Migration

​Overview

​Log Level

​LOG_LEVEL

​Output Format

​LOG_FORMAT

​File Logging

​SAVE_LOG_FILE

​LOG_FILE_NAME

​LOG_FILE_PATH

​File Rotation (v3)

​LOG_MAX_SIZE

​LOG_MAX_BACKUPS

​Slack Notifications

​SLACK_TOKEN

​SLACK_CHANNEL_ID

​NOTIFICATIONS_SLACK_ENABLED

​Legacy Notification Levels (v2)

​NOTIFICATION_FATAL_LOG

​NOTIFICATION_ERROR_LOG

​NOTIFICATION_WARNING_LOG

​NOTIFICATION_INFO_LOG

​NOTIFICATION_SUCCESS_LOG

​Configuration Priority

​Environment Configuration Examples

​Development Environment

​Staging Environment

​Production Environment

​Docker Configuration

​Kubernetes Configuration

​Loading Environment Variables

​v2 API (Automatic)

​v3 API (Manual)

​Next Steps

Build docs developers (and LLMs) love