Packages, Testing and Tooling

Go comes with a comprehensive built-in toolchain that handles formatting, testing, vetting, building, and dependency management. This lesson covers the package system, the testing framework, and the essential Go tools every developer should know.

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Packages

Package Basics

Every Go file belongs to a package:

package math   // this file belongs to the "math" package

Concept	Description
Package	A directory of Go files compiled together
main package	Special — defines an executable program
Exported names	Start with an uppercase letter (e.g., Println)
Unexported names	Start with a lowercase letter (e.g., helper) — private to the package

Package Organisation

myproject/
├── go.mod
├── main.go              # package main
├── server/
│   ├── server.go        # package server
│   └── server_test.go   # tests for package server
├── model/
│   └── user.go          # package model
├── handler/
│   ├── user.go          # package handler
│   └── user_test.go
└── internal/
    └── auth/
        └── auth.go      # package auth (only importable within myproject)

The internal Directory

The internal directory restricts package visibility: