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: conf_gcs.go
    path of file: ./repos/goofys/api/common
    
    the code of the file until where you have to start completion: package common

import (
	"context"
	"golang.org/x/oauth2/google"
)

type GCSConfig struct {
	Credentials *google.Credentials
	ChunkSize   int // determine the size of chunks when uploading a file to GCS
}

const (
	defaultGCSChunkSize int = 64 * 1024 * 1024
)

// NewGCSConfig returns a GCS Config.
func NewGCSConfig() *GCSConfig {
	// Credentials will be checked when initial
    
func NewGCSConfig() *GCSConfig {
	// Credentials will be checked when initializing GCS bucket to create an authenticated / unauthenticated client
	// We allow nil credentials for unauthenticated client.
	credentials, err := google.FindDefaultCredentials(context.Background())
	if err == nil {
		// authenticated config
		return &GCSConfig{
			ChunkSize:   defaultGCSChunkSize,
			Credentials: credentials,
		}
	} else {
		log.Debugf("Initializing an unauthenticated config: %v", err)
		// unauthenticated config
		return &GCSConfig{
			ChunkSize: defaultGCSChunkSize,
		}
	}
}