The Builder design pattern is a creational design pattern that is used to construct complex objects step by step. It separates the construction of an object from its representation, allowing the same construction process to create different representations.

The key idea behind the Builder pattern is to have a separate builder object responsible for constructing the product. The builder object defines a series of steps or methods to construct different parts of the product, and a method to retrieve the final constructed object.

The main components of the Builder pattern are:

• Product: It represents the complex object being constructed. It can be a composite of multiple parts or attributes.
• Builder: It is an interface that defines the steps or methods to build the product. Each method corresponds to a specific part of the product construction process.
• ConcreteBuilder: It is a concrete implementation of the Builder interface. It implements the methods defined in the builder interface and keeps track of the product being constructed.
• Director: It controls the construction process using the builder. It provides a higher-level interface for constructing the product, hiding the details of individual construction steps.

The Builder pattern allows you to construct objects step by step, providing more flexibility and control over the construction process.
It helps to avoid telescoping constructors or large numbers of constructor parameters, making the code more readable and maintainable.
It also allows for the creation of different variations of the product by using different builders.
The Builder pattern is particularly useful when you have complex objects with multiple optional or mandatory parameters, and you want to separate the construction logic from the final product.
It promotes code reusability and maintainability by encapsulating the construction process in a separate builder object.

In this example, we have a Product struct representing the final object to be built.
The Builder interface defines the steps required to build the product, including BuildPart1(), BuildPart2(), BuildPart3(), and GetResult().
The ConcreteBuilder struct implements the Builder interface.
It has its own instance of the product and implements each step of the building process.
The Director struct controls the construction process using a builder. It calls the builder's methods in a specific order to construct the product.
In the main function, we create a ConcreteBuilder instance and a Director instance.
We then use the director to construct the product by calling the builder's methods.
Finally, we retrieve the constructed product using GetResult() and print it.
The output of the program will be:

{Part 1 42 true}

This demonstrates how the Builder pattern separates the construction of a complex object from its representation.
The director controls the building process, while the concrete builder implements the steps to construct the object.
This allows for more flexibility and easier extension of the construction process, as well as the ability to construct different variations of the final object.