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: openvpn.go
    path of file: ./repos/gluetun/internal/configuration/sources/files
    
    the code of the file until where you have to start completion: package files

import (
	"fmt"

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

const (
	// OpenVPNClientKeyPath is the OpenVPN c
    
func (s *Source) readOpenVPN() (settings settings.OpenVPN, err error) {
	settings.Key, err = readPEMFile(OpenVPNClientKeyPath)
	if err != nil {
		return settings, fmt.Errorf("client key: %w", err)
	}

	settings.Cert, err = readPEMFile(OpenVPNClientCertificatePath)
	if err != nil {
		return settings, fmt.Errorf("client certificate: %w", err)
	}
	settings.EncryptedKey, err = readPEMFile(openVPNEncryptedKey)
	if err != nil {
		return settings, fmt.Errorf("reading encrypted key file: %w", err)
	}

	return settings, nil
}