logging

Logging

The logging package provides a simple, flexible, and color-coded logging system for Golang. Below are the main features and methods of the package:

Logger Constructor

• NewLogger(prefix string, minLevel LogLevel, output io.Writer) *Logger:
  Creates a new logger instance.
  • prefix: A string prefix added to all log messages.
  • minLevel: The minimum log level to output (DEBUG, INFO, WARN, ERROR). Messages below this level are ignored.
  • output: The destination for log output (e.g., os.Stdout, os.Stderr, or any io.Writer). Defaults to os.Stdout if nil.

Log Levels

• DEBUG: Used for detailed debug information.
• INFO: General informational messages.
• WARN: Warnings about potential issues.
• ERROR: Critical errors.

Logger Methods

• Info(message string):
  Logs an informational message with the log level INFO.

• Debug(message string):
  Logs a debug message with the log level DEBUG.

• Warn(message string):
  Logs a warning message with the log level WARN.

• Error(message string):
  Logs an error message with the log level ERROR.

Key Features

• Color-Coded Logs:
  Log messages are color-coded based on the log level:

  • DEBUG: Green
  • INFO: Blue
  • WARN: Yellow
  • ERROR: Red

• Timestamped Logs:
  Each log message includes a timestamp in the format YYYY-MM-DD HH:MM:SS.

• Log Filtering by Level:
  Logs below the specified minimum level (minLevel) are ignored.

• Custom Output:
  Logs can be directed to any io.Writer, allowing flexible output destinations (e.g., files, network connections).

• Disable Colors:
  The disableColors field in the Logger struct can be set to true to disable color codes (useful for testing or plain-text logs).

Redaction

The logging package can redact sensitive values before writing logs. Two methods are provided:

• SetRedactionRules(rules map[string]string)

  • Treats each map key as a literal pattern prefix (e.g., password: or api_key=).
  • Matches the key plus the following non-space characters and replaces them with the key concatenated with the provided replacement.
  • Example: {"password:": "***REDACTED***"} turns password:secret into password:***REDACTED***.

• SetRedactionRegex(patterns map[string]string) error

  • Accepts full regular expressions as keys and replacement strings as values.
  • Compiles each regex and returns an error if any pattern is invalid.
  • The replacement string replaces the matched substring.

Notes

• If the minLevel is set to DEBUG, all log messages will be displayed.
• Logs are automatically flushed to the configured output as soon as they're written.
• To log without colors (e.g., for testing), set the disableColors field to true in the Logger instance.

Examples:

For examples of each function, please checkout EXAMPLES.md