You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: log.go
    path of file: ./repos/gluetun/internal/configuration/sources/env
    
    the code of the file until where you have to start completion: package env

import (
	"errors"
	"fmt"
	"strings"

	"github.com/qdm12/gluetun/internal/configuration/settings"
	"github.com/qdm12/log"
)

func (s *Source) readLog() (log settings.Log, err error) {
	log.Level, err = s.readLogLevel()
	if
    
func parseLogLevel(s string) (level log.Level, err error) {
	switch strings.ToLower(s) {
	case "debug":
		return log.LevelDebug, nil
	case "info":
		return log.LevelInfo, nil
	case "warning":
		return log.LevelWarn, nil
	case "error":
		return log.LevelError, nil
	default:
		return level, fmt.Errorf(
			"%w: %q is not valid and can be one of debug, info, warning or error",
			ErrLogLevelUnknown, s)
	}
}