Split Go code into packages when files grow large, logic diverges, or you need to hide internal implementation details.
Split your Go code into multiple packages when files exceed 500 lines, when functionality serves distinct logical domains, or when you need to enforce encapsulation by hiding unexported symbols. Create a new directory for the package, move related files there, and update import paths to reflect the new structure.
mkdir internal/auth
mv auth.go internal/auth/
# Update imports in main.go
# import "your/module/internal/auth"
Think of packages like folders in a filing cabinet. You keep related documents together in one folder so you can find them easily and keep unrelated papers separate. In Go, splitting code into packages helps you organize large projects, prevents naming conflicts, and lets you hide internal details that other parts of your code shouldn't touch.