code: func Detect() (string, error) {
  	shell := os.Getenv("SHELL")
  
  	if shell == "" {
  		fmt.Printf("The default lines below are for a sh/bash shell, you can specify the shell you're using, with the --shell flag.\n\n")
  		return "", ErrUnknownShell
  	}
  
  	return filepath.Base(shell), nil
  }
docs: // Detect detects user's current shell.