intro_to_go

The aim of this lesson is to cover the basics of the Go programming language

Some important things to know about Go:

• It was designed at Google by Robert Griesemer, Rob Pike, and Ken Thompson
• Syntactically similar to C
• It is not exactly an object oriented language
  • No classes, but there are structures
  • You can define methods for these structures
  • Still similar to OOP
• How to write Go code
  • The go tool requires you to organize your code in a specific way
  • We will cover the basics in this lesson, but use this for further reading or as a reference

Getting started

First, head to the official Go website and download the latest version of Go

I would recommend using VS Code with the Go extension for development. That is what we'll be using in this lesson.

• We will compile and run Go in the command line
• There is a Go IDE, GoLand by JetBrains, as well if you are interested (but we won't be really covering that)

Your first Go program

Open up the command line, and navigate to your Go workspace:

• C:\Users\YourName\go\src on Windows
• $HOME/go/src on Unix based systems
• The location of your workspace can be changed. See "How to write Go code" above

Make a new directory (folder) called shopping

Navigate into shopping and create a file called main.go. We will write the following code

package main

import (
	"fmt"
)

func main() {
	fmt.Println("Wow I did it")
}

To run this, type go run main.go into the command line

Congrats, you've written your first Go program!

Getting some input

An important part of this application is reading in user input, so we'll learn about that next

package main

import (
	"fmt"
)

func main() {
	fmt.Println("What is your name?")

	var name string
	fmt.Scanln(&name)

	fmt.Println("Hello,", name)
}

Again, type go run main.go into the command line to run this

Adding some structures

Now that basic I/O has been covered, let's move on to structures

Here's a basic structure that we're going to be using:

type product struct {
    name string
    cost int
}

Now we can create a new product:

func main() {
	p := product{
		name: "Brick",
		cost: 10,
	}

	fmt.Println(p.name, "costs $", p.cost)
}

Using structs, we can begin to build a more complex application

Creating the store

We're going to start building our store application

func main() {
	brick := product{name: "brick", cost: 10}
	corn := product{name: "corn", cost: 6}
	gamecube := product{name: "gamecube", cost: 100}

	inventory := []product{brick, corn, gamecube}

	fmt.Println("Welcome to the store!")
	fmt.Println("Options:")
	fmt.Println("(i)nventory")
	fmt.Println("(b)uy item")
	fmt.Println("(a)dd item")
	fmt.Println("(q)uit")

	var choice string
	fmt.Scanln(&choice)

	for choice != "q" {
		switch choice {
		case "i":
			for _, p := range inventory {
				fmt.Println("name:", p.name)
				fmt.Println("cost:", p.cost)
				fmt.Println()
			}
			break
		case "b":
			var toBuy string
			fmt.Print("What product would you like to buy? ")
			fmt.Scanln(&toBuy)

			loc := -1
			for i, p := range inventory {
				if p.name == toBuy {
					loc = i
				}
			}

			if loc == -1 {
				fmt.Println("Item isn't in stock")
			} else {
				inventory = append(inventory[:loc], inventory[loc+1:]...)
			}

			break
		case "a":
			var newName string
			fmt.Print("Enter a product name: ")
			fmt.Scanln(&newName)

			var newCost int
			fmt.Print("Enter a cost: ")
			fmt.Scanf("%d", &newCost)

			inventory = append(inventory, product{name: newName, cost: newCost})
			break
		}

		fmt.Println("Welcome to the store!")
		fmt.Println("Options:")
		fmt.Println("(i)nventory")
		fmt.Println("(b)uy item")
		fmt.Println("(a)dd item")
		fmt.Println("(q)uit")
		fmt.Scanln(&choice)
	}
}

The completed code can also be found in the main.go file in this repository

Further reading

If you are interested in learning more about Go, I would recommend checking out these resources:

• A Tour of Go
• Go by Example

Another great resource in the official docs for when you're more familiar with the language:

• Effective Go