Go Packages & Modules

What is a Package?

A package is a way to organize and reuse code in Go.

Every Go file belongs to a package.

Built-in Packages

Go provides many built-in packages like fmt, math, and time.

You import them using the import keyword.

Creating Custom Packages

You can create your own packages by placing Go files in a folder.

The package name must match the folder name.

Importing Custom Packages

You can import your custom package using its module path.

Then call exported functions (capitalized names).

Exported vs Unexported

In Go, names starting with a capital letter are exported (public).

Lowercase names are private to the package.

What is a Module?

A module is a collection of packages managed together.

It defines your project and its dependencies.

go.mod File

The go.mod file tracks your module name and dependencies.

It is automatically created when you run go mod init.

Managing Dependencies

Go modules automatically handle external libraries.

Use go get to install packages.

Project Structure Example

A typical Go project is organized using packages and modules.

Why Packages & Modules Matter

They help you organize code and build scalable applications.

• Reusable code
• Clean project structure
• Dependency management

Common Mistakes

Be careful with these:

• Incorrect import paths
• Forgetting to export functions (capital letters)
• Not initializing modules

Practice

Create a custom package with a function and import it into main.

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