Data Types in Golang7 min read

Data types in golang define the type of data a variable is going to store. In Go, the data types are divided into four categories –

1. Basic – Numbers, strings, booleans
2. Aggregate – Arrays, Structs
3. Reference – Pointers, slices, maps, functions, and channels
4. Interface

In this tutorial, we will be looking at basic and aggregate data types.

1. Basic Data Types in Golang

The basic data types in go include the below data types,

1. Numbers
2. Booleans
3. Strings

A. Numbers

In go, numbers are divided into 3 subcategories,

a. Integers

Integers are like whole numbers but they also include negative numbers. Both signed and unsigned integers are available in go into four different sizes as shown in below table,

b. Floating point numbers

The floating-point numbers include the decimal numbers and in go, they are divided into below 2 categories

c. Complex numbers

A complex number is one that can be written as a + bi, with a and b being real values and ‘i’ being an imaginary number. In go, the complex numbers are divided into 2 parts as shown in the below table,

The type of a number can be printed in the output of a go program with the symbol %T.

Example:

// Go program to illustrate the use of numbers
package main
import "fmt"

func main() {
  x:= 12345 // integer value
  y:= 86.72 // float value
  z:= complex(4, 8) // complex value
  
  fmt.Printf("the type of x is %T and the value of x = %d", x, x)
  fmt.Printf("\nthe type of y is %T and the value of y = %f", y, y)
  fmt.Printf("\nthe type of z is %T and the value of z = ", z)
  fmt.Println(z)
}

Output:

C:\Users\Hiberstack\GoPrograms>go run Numbers.go
the type of x is int and the value of x = 12345
the type of y is float64 and the value of y = 86.720000
the type of z is complex128 and the value of z = (4+8i)

B. Booleans

Only one bit of information, true or false, is represented by the boolean data type. The values of type boolean are not transformed to any other type, either automatically or explicitly.

Example:

// Go program to illustrate
// the use of booleans
package main
import "fmt"

func main() {
  str1 := "abc"
  str2 := "ABC"
  str3 := "abc"

  result1:= str1 == str2
  result2:= str1 == str3

  // Display the result
  fmt.Println(result1)
  fmt.Println(result2)

  // Display the type of
  // result1 and result2
  fmt.Printf("The type of result1 is %T and " +
    "the type of result2 is %T", result1, result2)
}

Output:

C:\Users\Hiberstack\GoPrograms>go run BooleanDemo.go
false
true
The type of result1 is bool and the type of result2 is bool

C. Strings

A string data type is a sequence of characters. Unlike JavaScript, strings are defined between double quotes “…” rather than single quotes. By A string data type is a sequence of characters. Unlike JavaScript, strings are defined between double quotes “…” rather than single quotes. Strings are immutable, i.e. once you create a string it cannot be changed again. By default, strings in Go are encoded in UTF-8. In most circumstances, you won’t have to bother about encoding because UTF-8 supports the ASCII character set.

Let us look at an example of how to define a string in go.

Example:

//Program to eillustrate use of String in go
package main
import "fmt"

func main(){
  var s string
  s = "Hellow World"
  fmt.Println(s)
}

Output:

C:\Users\Hiberstack\GoPrograms>go run StringDemo.go
Hellow World

2. Aggregate Data Types in Golang

Aggregate data types in go are divided into 2 subcategories as below,

1. Arrays
2. Structs

A. Arrays

An array is nothing but a collection of similar types of elements. Here, the similar type of elements refers to the values having similar data types. For example, we can use Arrays to store the marks of a student. Marks are the float values. Arrays have a fixed length and therefore you need to define their length at the time of array declaration.

You can store 0 or n number of elements in an array. The array’s items are indexed using the [] index operator and their zero-based position, thus the first element’s index is array[0] and the last element’s index is array[len(array)-1].

Declaring an array –

In go, we can declare arrays in 2 ways,

1. Using var keyword

var array_name[length]datatype

Or

var array_name[length]datatype{item1, item2,…,itemN}

Example:

// Go program to illustrate how to
// create an array using the var keyword
// and accessing the elements of the
// array using their index value
package main
import "fmt"

func main() {
  // Creating an array of string type
  // Using var keyword
  var myarr[3]string

  // Elements are assigned using index
  myarr[0] = "Hiberstack"
  myarr[1] = "Go"
  myarr[2] = "lang"

  // Accessing the elements of the array
  // Using index value
  fmt.Println("Elements of Array:")
  fmt.Println("Element 1: ", myarr[0])
  fmt.Println("Element 2: ", myarr[1])
  fmt.Println("Element 3: ", myarr[2])
}

Output:

C:\Users\Hiberstack\GoPrograms>go run ArrayDemo1.go
Elements of Array -
Element 1:  Hiberstack
Element 2:  Go
Element 3:  lang

2. Using shorthand

array_name:= [length]Type{item1, item2, item3,...itemN}

Example:

// Go program to illustrate how to create
// an array using shorthand declaration
// and accessing the elements of the
// array using for loop
package main
import "fmt"

func main() {
  //Shorthand declaration of array
  arr:= [4]string{"Hiberstack", "go", "lang", "tutorial"}
  
  // Accessing the elements of
  // the array Using for loop
  fmt.Println("Elements of the array -")
  for i:= 0; i < 3; i++{
    fmt.Println(arr[i])
  }
}

Output:

C:\Users\Hiberstack\GoPrograms>go run ArrayDemo2.go
Elements of the array -
Hiberstack
go
lang

B. Structs

A Struct or Structure in golang is a user-defined data type that allows a user to group elements of different data types together. For example, we can create a structure for a person as a person has different attributes such as name, address, contact, age, etc.

Syntax:

type Person struct {
  name string 
  address string
  contact int
  age int
}

The type keyword creates a new type in the scenario above. It’s followed by the type name (Person) and the keyword struct to show that we’re creating a struct. Within the curly braces of the struct is a list of several fields. A name and a type are assigned to each field.

Declaring a struct –

Syntax: var a Person

The above will declare a struct by the name ‘a’ that has a type Person.

Example:

//Go program to illustrate use of Struct
package main
import "fmt"

type Person struct {
  name string
  address string
  contact, age  int //declaring multiple variables at a time
}

func main() {
  person1:= Person{"John", "Canada", 2379283, 28}
  person2:= Person{name: "Sean", address: "USA", contact: 12345678, age: 50}
  
  fmt.Println("Person1 -\n", person1) //printing all the values of person1
  fmt.Println("Name of Person2 - ", person2.name)
  fmt.Println("Age of Person2 - ", person2.age)
}

Output:

C:\Users\Hiberstack\GoPrograms>go run StructDemo.go
Person1 -
 {John Canada 2379283 28}

Name of Person2 -  Sean
Age of Person2 -  50