1. Introduction

In this tutorial, we will go over the basics of creating and using functions in Go. A function is a block of code that performs a specific task and can be called by name. Functions are fundamental to any programming language as they allow us to encapsulate logic and reuse it in different parts of our program.

By the end of this tutorial, you should be able to:
- Understand what functions are and why we use them.
- Create your own functions in Go.
- Call these functions from other parts of your code.
- Use parameters to pass data into your functions.

Prerequisites:
- Basic understanding of Go syntax.
- Installed Go environment on your machine.

2. Step-by-Step Guide

A function in Go is defined using the func keyword, followed by the function's name, a list of parameters (if any), the return type (if any), and a block of code surrounded by curly braces {}.

Here’s the basic syntax of a function in Go:

func functionName(parameter1 type, parameter2 type) returnType {
  // Function Body
}

The function's name is functionName, and it takes two parameters, parameter1 and parameter2, of types type. It returns a value of type returnType.

You can call this function from other parts of your code by its name and providing the required parameters:

functionName(value1, value2)

Best practices and tips:
- Always give your functions descriptive names that clearly indicate what they do.
- Keep your functions small and focused on a single task.
- Use parameters to make your functions more flexible and reusable.

3. Code Examples

Let's take a look at a practical example:

// Define a function that adds two integers and returns the result
func add(x int, y int) int {
  return x + y
}

// Call the function
result := add(1, 2)

// Print the result
fmt.Println(result)  // Outputs: 3

In this example, we define a function called add that takes two parameters, x and y, and returns their sum. We then call this function with the values 1 and 2, and print the result.

4. Summary

In this tutorial, we've learned how to create and use functions in Go. We've seen how to define our own functions, call them from other parts of our code, and use parameters to pass data into our functions.

Next steps for learning:
- Learn more about different types of functions in Go, such as variadic functions and anonymous functions.
- Learn about error handling in Go functions.

Additional resources:
- A Tour of Go
- Go by Example

5. Practice Exercises

1. Write a function that multiplies two numbers and returns the result.
2. Write a function that takes a string as a parameter and prints it.
3. Write a function that takes an array of integers and returns the sum.

Here are the solutions:

1. Multiply function:

func multiply(x int, y int) int {
  return x * y
}

1. Print string function:

func printString(s string) {
  fmt.Println(s)
}

1. Sum array function:

func sumArray(arr []int) int {
  sum := 0
  for _, v := range arr {
    sum += v
  }
  return sum
}

Remember, the only way to get better at programming is by writing a lot of code. Keep practicing!