Introduction to Go

What is Go?

Go (often called Golang) is an open-source programming language developed at Google by Robert Griesemer, Rob Pike, and Ken Thompson. First released in 2009, Go was designed to address common criticisms of other languages while maintaining their positive characteristics.

Why Learn Go?

Go has become incredibly popular for building modern software. Here’s why:

Who Uses Go?

Go’s Key Features

Installing Go

Let’s get Go installed on your computer.

Step 1: Download Go

1. Visit go.dev/dl
2. Download the installer for your operating system
3. Run the installer and follow the prompts

Step 2: Verify Installation

Open your terminal (Command Prompt on Windows, Terminal on macOS/Linux) and run:

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go version

You should see output like:

go version go1.21.0 darwin/amd64

Step 3: Check Your Environment

Run this command to see your Go environment:

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go env GOPATH GOROOT

• GOROOT: Where Go is installed
• GOPATH: Your workspace for Go projects (usually ~/go)

Your First Go Program

Let’s write the classic “Hello, World!” program.

Using the Go Playground

The fastest way to try Go is the Go Playground - an online editor that runs Go code in your browser.

Visit the playground and enter this code:

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package main

import "fmt"

func main() {
    fmt.Println("Hello, World!")
}

Click “Run” and you’ll see:

Hello, World!

Creating a Local Project

Let’s create a proper Go project on your computer.

Step 1: Create a project directory

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mkdir hello
cd hello

Step 2: Initialize a Go module

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go mod init hello

This creates a go.mod file that tracks your project’s dependencies.

Step 3: Create the main file

Create a file named main.go with the following content:

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package main

import "fmt"

func main() {
    fmt.Println("Hello, World!")
    fmt.Println("Welcome to Go in 30 Days!")
}

Step 4: Run your program

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go run main.go

Output:

Hello, World!
Welcome to Go in 30 Days!

Understanding the Code

Let’s break down what we wrote:

Package Declaration

Every Go file starts with a package declaration:

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package main

• package main is special - it tells Go this is an executable program
• Other packages (like fmt) are libraries that provide functionality

Import Statement

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import "fmt"

• import brings in code from other packages
• fmt is the formatting package for input/output
• You can import multiple packages:

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import (
    "fmt"
    "time"
)

The main Function

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func main() {
    // code here
}

• func declares a function
• main is the entry point - Go starts here
• {} contains the function body

Printing Output

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fmt.Println("Hello, World!")

• fmt.Println prints a line of text
• Text in quotes is a string
• Println adds a newline at the end

Go Commands

Go comes with powerful built-in tools:

Building an Executable

Instead of go run, you can build a standalone executable:

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go build -o hello

This creates an executable file called hello (or hello.exe on Windows) that you can run directly:

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./hello

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GOOS=linux GOARCH=amd64 go build -o hello-linux

Code Formatting with go fmt

Go has a standard code formatter. Run it on your code:

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go fmt main.go

This automatically formats your code to Go’s standard style. No more debates about tabs vs spaces!

Summary

Today you learned:

• Go is a simple, fast, and concurrent programming language
• How to install Go and verify your installation
• How to write and run your first Go program
• The structure of a Go program (package, import, main)
• Essential Go commands (go run, go build, go fmt)

Practice Exercise

Before moving on, try these exercises:

1. Modify the hello program to print your name
2. Add a third fmt.Println statement
3. Try using fmt.Print instead of fmt.Println - what’s different?
4. Build an executable and run it

Next Steps

Tomorrow, we’ll dive into variables and data types - the foundation of every Go program!

Now, complete the quiz below to test your knowledge and unlock Day 2!