Let’s GO! Part 3: Hello, world!

Hello, world!

Alright let’s do it!

Things to know before we start:

• Any files containing the GO codes should have .go extension.
• Any .go file should start with a package decorator which we’ll see in a moment. (You know, it should say what package it belongs to.)
• Any applications written in GO should have a main function that is the entry point of your application.
• Functions are defined with the func keyword. Yeah the language tries so hard to look cool. :))
• You can import packages inside other packages by using the import keyword.

Create a directory called hello-world or whatever name you prefer, and then open your IDE/Text Editor inside that directory. Create a new file called main.go with the following code inside it:

Hello, world!

What’s happening up there?

• At line 1, we’re defining our package name which is main. It can be any other names but we do it like this for convention.
• At line 3, we’re importing the standard I/O package of GO which is named fmt.
• At line 5 we’re defining a function called main with no arguments which is necessary to exist in every GO program.
• And finally at line 6 which is our function’s body, we’re calling the Println method of the fmt package which is responsible for printing a single line to the console.

Note1: The GO language server will automatically add the line 3 while writing line 6 if you forget to mention it and if you have enabled Autocomplete Unimported Packages which was talked about in Part 2.

Note2: You can replace fmt package with log package and they’re almost the same. You can see how they differ here.

Run it:

Open a terminal window at the root level of the project where the main.go file exists and simply run:

go run main.go

You should now see the Hello, world! printed to the console.

Compile it:

Now we said that GO is a compiled language. So why don’t we try to compile what we did now to see the magic? Run this line in your terminal:

go build -o hw main.go

You’re basically telling the official GO compiler to compile the entry point of your application which is main.go in this case into a file named hw. Now that’ll work for Linux and macOS but if you tend to compile it for Windows just replace hw with hw.exe. Then you can run the compiled file with ./hw on macOS and Linux and ./hw.exe on Windows.

Alright you did it! Was it hard? Nah I don’t think so. Let’s progress into more concepts and we’ll see what happens next.

Next:

Let’s GO! Part 4: Variables and Constants

Previous:

Let’s GO! Part 2: Setup

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