How To Cast In Golang

Go Programming

As a programmer who has been working with Golang for several years now, I have found the casting feature to be incredibly useful in many different scenarios. In this article, I will guide you through the process of casting in Golang, while also sharing some personal insights and commentary along the way.

What is Casting?

Casting is a process in which we convert a variable from one data type to another. In Golang, casting can be done using the syntax: newDataType(variable). It allows us to change the type of a variable temporarily or permanently, depending on our needs.

Casting Basic Data Types

Let’s start by looking at how casting works with basic data types in Golang. For example, suppose we have an integer variable num, and we want to convert it to a float:

num := 42
floatNum := float64(num)

In the above code snippet, we are casting the variable num to a float64 by using the float64() function. It is important to note that casting doesn’t change the original value of the variable, but rather creates a new variable of the desired type.

Similarly, we can cast a float to an integer:

floatNum := 3.14
intNum := int(floatNum)

In this case, we are casting the float variable floatNum to an integer using the int() function. Again, the original value of the variable remains unchanged.

Casting Pointers

Golang also allows us to cast between different pointer types. Let’s say we have a pointer to an integer, and we want to cast it to a pointer to a float:

var num int = 42
var ptrToInt *int = &num
ptrToFloat := (*float64)(unsafe.Pointer(ptrToInt))

In the above code, we first declare a pointer to an integer named ptrToInt. Then, using the unsafe.Pointer type, we cast the ptrToInt to a pointer to a float64. This type of casting is considered unsafe because it bypasses Go’s type safety mechanisms. Therefore, it should be used with caution and only when absolutely necessary.

Casting Structs

When it comes to casting structs, Golang provides a simple and straightforward way to convert between compatible struct types. Let’s say we have two struct types named Person and Employee:

type Person struct {
Name string
Age int

type Employee struct {
Name string
Age int
Position string

In the above example, both Person and Employee have the same fields but with an additional Position field in the Employee struct. We can cast a Person variable to an Employee variable, but not the other way around:

person := Person{Name: "John Doe", Age: 30}
employee := Employee(person)

By using the Employee() constructor, we can cast the person struct to an employee struct. However, it’s important to note that the additional Position field in the Employee struct will not be initialized with this casting.


Casting is a powerful feature in Golang that allows us to convert variables from one type to another. Whether it’s casting basic data types, pointers, or structs, Golang provides us with the necessary tools to perform these conversions. However, it’s important to use casting judiciously and be aware of any potential risks or limitations associated with it.

Throughout my time working with Golang, I have found casting to be an invaluable tool in solving various programming challenges. I hope this article has provided you with a comprehensive understanding of how to cast in Golang, and that it will empower you to leverage this feature effectively in your own projects.