Setup: install Go and run your first program

You need three things: Go itself, a folder to work in, and a text editor (VS Code with the official Go extension works well).

1. Install Go

Download the installer for your system from go.dev/dl and follow the steps, then open a new terminal and check:

go version

You should see something like this (this course was written and every example run with Go 1.27; anything from Go 1.22 onward behaves the same):

go version go1.27.2 linux/amd64

2. Make a project folder

mkdir hello-go
cd hello-go
go mod init hello-go

go mod init creates a small file called go.mod. It names your module (your project) and lists the third-party packages you use. You do this once per project.

3. Write and run

Create main.go with the program from Session 1, then:

go run main.go      # build + run + clean up
go build            # produce an executable file named after the module
go fmt ./...        # format all code the standard way
go vet ./...        # catch suspicious code

The course code

Every example in this course is a plain .go file in a folder per session. Each is run on its own with go run file.go, because several small programs share a folder and each has its own main. The output you see on the pages was captured by running the files, not typed by hand.

Note

Sessions 10 and 13 use outside packages (yaml, logrus, sqlite). Inside a module, run go get <package> once, or go mod tidy, and Go downloads them.

How this course follows the 40 Days of Go repository

The original repository has working code for 13 topics. This course turns each into a session and fills in the topics the syllabus names but the repository does not yet cover:

Repository folder	Session
01.basics	1 Hello & basics, 2 Functions, 3 Arrays & slices, 4 Maps
02.structs	5 Structs & JSON
03.pointers	6 Pointers
(syllabus: error handling, retry logic)	7 Errors
04.files	8 Files
05.command_line, 06.file_finder	9 Command line
07.logging	10 Logging & config
08.http	11 HTTP
09.todo-api	12 Todo API
10.todo_db	13 Database
11.gortn	14 Goroutines
12.waitgrp	15 WaitGroup
13.mutx	16 Mutex
(syllabus: goroutines & channels)	17 Channels & select
(testing)	18 Testing