Summary  
This chapter covers how to declare, define, and invoke reusable code blocks (functions) using the `func` keyword and how to call them within other functions.  

General domain of usage  
Displaying user notifications in web applications.

A function is a reusable block of code that accomplishes a specific task. To declare a function, you can use the `func` keyword. Here is the syntax for defining a basic function:

```go
func functionName() {
    // Code to be executed
}
```

Below is a straightforward example of a function created using the provided format:



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Here is a visual representation illustrating the declaration of a function:


If we incorporate the code provided above into our program, it will transform into a reusable component that we can invoke as often as needed by calling the function. To call or execute a function, use the following syntax:

```
functionName()
```

Here is an example of a comprehensive program that employs the previously mentioned function:


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Within the `main` function, we utilized `sayHelloWorld()` to invoke the function. You can replicate this call as many times as needed to execute it repeatedly:


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Select the appropriate line of code to call the defined function:

This course is an introduction to the Go language for absolute beginners. It covers all the essential topics that are necessary to start coding in Go.

Declaring and Defining Functions