File Server in go

1. Write: create a file, or update the file’s contents if it already exists.
   Usage : write <filename> <numbytes> [<exptime>]\r\n<content bytes>\r\n
   Response : OK <version>\r\n
2. Read: Given a filename, retrieve the corresponding file.
   Usage: read <filename>\r\n
   Response : CONTENTS <version> <numbytes> <exptime>\r\n <content bytes>\r\n
3. Compare and swap. This replaces the old file contents with the new content provided the version is still the same.
   Usage: cas <filename> <version> <numbytes> [<exptime>]\r\n <content bytes>\r\n
   Response : OK <version>\r\n
4. Delete file
   Usage: delete <filename>\r\n
   Response: OK\r\n

1. ERR_VERSION\r\n (the contents were not updated because of a version mismatch)
2. ERR_FILE_NOT_FOUND\r\n (the filename doesn’t exist)
3. ERR_CMD_ERR\r\n (the command is not formatted correctly)
4. ERR_INTERNAL\r\n (any other error you wish to report that is not covered by the rest)

1. If the power fails, then all the data is lost