Refactoring for upgrading to gup version 1.0.0.

[nao1215]

The gup command has been used by more people than expected. However, the implementation and design of the gup command have a very low level of completion for the following three reasons:

1. It was implemented by developers who were unfamiliar with golang at the time.
2. There was a major forced change from the initial design.
3. Functionality was added without limitations.

Due to these reasons, the gup command has become difficult to maintain, especially in terms of writing test code.Therefore, a complete refactoring will be performed before upgrading to version 1.0.0.