Apply the GO style to the project's directory layout.

[marcos-wz]

The go modules suggest putting the packages at the top/root level as much as possible.

Advantages:

• Encapsulate each package-specific logic
• Isolated: keeps dependencies logic/maintenance within the package's scope and avoids importing circle issues
• Focus on the Dependency injection pattern
• Ready for implementation of the SOLID principles
• Maintainable code
• Simple, readable layout.