Go basics

In this lesson, we will cover the fundamentals of the Go programming language.

• Syntax rules; use of curly braces, case-sensitivity, comments
• Modules
• Variables, types and constants
• Data types
• Visibility
• Collections
• Numbers
• Functions
• Pointers and references
• Control structures
• panic, defer
• Error handling design pattern
• Packages to organize, share and use code

As a practical exercise (well, many exercises) along the way, we are going to build a command line tool that can compress and decompress bitmap images.

Language types

Basic rules

• We use .go files
• Code blocks in {}
• No styling freedom
• We do have semi-colon to separate sentences
• They are optional though
• Case-senstive
• Strongly typed
• NOT an object-oriented language
• No classes, no inheritance
• No exceptions, no try-catch

• We have one file acting as the entry point with a main function
• A folder is a package
• Packages can have simple names (utilities) or URLs (github.com/username/project)
• Within one .go file, we can have:
  • Variables
  • Functions
  • Type declarations
  • Method declarations

Modules

• A module is a group of packages
• You can think of it as a project
• Modules contain a go.mod file that contains the module name, configuration and metadata (about dependencies)

Note: While having a module for a directory is not mandatory for Go code to run, modules is a way to organize your code and dependencies into chunks much like a small project. By creating the go.mod file, you are creating a module. The real power of modules comes into light when you start to use dependencies as a module helps you manage them.

CLI

It manipulates the module

• go mod init -> initializes the module
• go build -> builds the module
• go test -> tests the module
• go run -> builds and runs the module
• go get -> retrieves dependencies

Creating a module

1. Create a new folder (e.g. gointro)
2. Run go mod init <module-name>

You will get a go.mod file with the module name and Go version the code is to be compiled in.

Very simple.

go.mod example:

module itu.com/bds/gointro

go 1.23

Running the module

go run .

If you are coming from JavaScript, the go.mod file is similar to the package.json file.

Similarly, if you are coming from Python, the go.mod file is similar to the requirements.txt. Or pyproject.toml file when using Poetry.

Workspaces

Kind of a "super module" that can be used to organize projects into multiple modules.

• Introduced in Go 1.18

It contains a go.work file that contains configuration and metadata—including which module to use.

The Go CLI manipulates the workspace.

Creating a workspace

1. Create a new folder
2. go work init <modules-directory>

The go work init command tells go to create a go.work file for a workspace containing the modules in the <modules-directory> directory.

For more details: https://go.dev/doc/tutorial/workspaces

go.work example:

go 1.23

use ./gointro

But really, modules and packages are all you are going to need.