Google Drive - Create a folder

GoogleDriveCreateFolder.swift

func createFolder(
    name: String,
    service: GTLRDriveService,
    completion: @escaping (String) -> Void) {
    
    let folder = GTLRDrive_File()
    folder.mimeType = "application/vnd.google-apps.folder"
    folder.name = name
    
    // Google Drive folders are files with a special MIME-type.
    let query = GTLRDriveQuery_FilesCreate.query(withObject: folder, uploadParameters: nil)
    
    self.driveService.executeQuery(query) { (_, file, error) in
        guard error == nil else {
            fatalError(error!.localizedDescription)
        }
        
        let folder = file as! GTLRDrive_File
        completion(folder.identifier!)
    }
}