Set go Slog Levels With An Environment Variable

The examples in the slog docs are pretty convoluted. Setting a log level via an environment variable's actually pretty simple. Here's the code. By default the code is silent, set LOG_LEVEL in your environment to one of the strings "INFO", "DEBUG", "WARN" or "ERROR" to enable that level of logging.

Note the function at the bottom called `getLogLevelFromEnv()` and that it's called in the HandlerOptions:

package main

import (
    "log/slog"
    "os"
    "strings"
)

func main() {
    opts := &slog.HandlerOptions{
        Level  : getLogLevelFromEnv(),
    }

    handler := slog.NewTextHandler(os.Stdout, opts)

    logger := slog.New(handler)
    logger.Debug("Debug message")
    logger.Info("Info message")
    logger.Warn("Warning message")
    logger.Error("Error message")

    // This message will not be logged since it's below the warning level
    logger.Debug("This debug message will not be logged")
    logger.Info("This info message will not be logged")

    // These messages will be logged
    logger.Warn("This is a warning message", "key", "value")
    logger.Error("This is an error message", "key", "value")
}

func getLogLevelFromEnv() slog.Level {
    levelStr := os.Getenv("LOG_LEVEL")
    switch strings.ToLower(levelStr) {
    case "debug":
        return slog.LevelDebug
    case "info":
        return slog.LevelInfo
    case "warn":
        return slog.LevelWarn
    case "error":
        return slog.LevelError
    default:
        return slog.Level(100) // Custom level higher than any standard level, so silent by default

    }
}