Go

This project is a minimal sample for Go Hello World application.

Download Installer

Go language requires compiler that compiles source files and runtime that executes compiled binary files. The executable for compiler and runtime is OS dependent so please download the installer of your choice.

• Windows
• MacOS
• Linux

After download, please follow the install instruction for your operating system.

Ensure Go executable in your PATH

The install instruction provides steps to incorporate Go runtime in system/user PATH to be accessible anywhere. Please make sure that the steps have been correctly performed by open up a terminal and run:

go version

If the version detail does not display, please ensure the go executable has been set up in your PATH according to install instruction

Hello World

A boring basic sample for a start which located under 01-helloworld directory

Build Hello World

Navigate to the clone project directory under 01-helloworld where main.go is located and run:

go build main.go

The command generates main file for go runtime to execute.

Run Hello World

At the location where main file is located, run command:

go run . main

The main by itself is an executable file which is able to execute directly with the command below without go

./main

Test Hello World

At the location where main file is located, run command:

bash test.sh

What's inside main.go

Some interesting things you can learn from a hello world app

Package

Package is a collection related go files with the rule is the first line of each go file is required to have the package name where it belongs to.

There are two types of package

• Executable [package main]
• Reusable [other packages]

The name of packages can also be different from the actual directory name where they are located.

Import

The import is declared to get access to functions and libraries defined in the target package. The name of target import package is required to surround with double quotes.

Function [func]

Function declaration uses keyword func followed by name of the function with parenthesis for the list of arguments if needed. A pair of open and end curly braces is used to begin and end function definition.

A key takeaway note for this basic hello world app is the function main is required as entry point of the executable. The main package can have as many files as it needs but there will be only ONE file with main function declaration.

Cards

Another sample project is about cards and it's located at 02-cards

Variable declaration

GO is strict type language therefore variable declaration requires explicit data type, however, the language is flexible and smart enough to be able to figure out data type at compile time by using some hint.

Declaring variable with explicit type

var var_name string = "a var"

Declaring variable without explicity type

var_name := "Data"

By using :=, GO will try to figure out from the data on the right hand to determine the data type at compile time. To reassign value to the variable, it is no longer required to use :=, only = is sufficient.

var_name = "Updated data"

Function with Return value [func]

A function can return value by using keyword return following by the returning value. Go requires explicit return type declaration by appending the data type next to parenthesis and before the begin curly braces.

func newCard() string {
	return "Five of Diamonds"
}

Slice and For Loop

Go uses square bracket to declare slice (array) with data type and the data inside curly braces.

cards := []string{"Ace of Diamonds", newCard()}

The append function can be used to add item into existing slice. The slice object returned by append function is new slice object with the appended item.

cards = append(cards, "a card")

Iteration though each item of slice can be done with for loop

for i, card := range cards {
	fmt.Println(i, card)
}