How to Initialize Struct in Go: Syntax and Examples

In Go, you can initialize a struct by using a struct literal with field names or by creating a variable and assigning values to its fields. You can also use the new keyword to create a pointer to a struct with zero values.

Syntax

There are several ways to initialize a struct in Go:

• Struct literal with field names: Specify values for each field by name.
• Struct literal without field names: Provide values in order, but this is less clear.
• Using new keyword: Creates a pointer to a struct with zero values.
• Declare variable and assign fields: Create an empty struct variable and set fields later.

go

type Person struct {
    Name string
    Age  int
}

// Struct literal with field names
p1 := Person{Name: "Alice", Age: 30}

// Struct literal without field names
p2 := Person{"Bob", 25}

// Using new keyword
p3 := new(Person) // p3 is *Person with zero values
p3.Name = "Charlie"
p3.Age = 40

// Declare variable and assign fields
var p4 Person
p4.Name = "Diana"
p4.Age = 22

Example

This example shows how to create and print structs initialized in different ways.

go

package main

import "fmt"

type Person struct {
    Name string
    Age  int
}

func main() {
    // Initialize with field names
    p1 := Person{Name: "Alice", Age: 30}

    // Initialize without field names
    p2 := Person{"Bob", 25}

    // Using new keyword
    p3 := new(Person)
    p3.Name = "Charlie"
    p3.Age = 40

    // Declare variable and assign fields
    var p4 Person
    p4.Name = "Diana"
    p4.Age = 22

    fmt.Println(p1)
    fmt.Println(p2)
    fmt.Println(*p3)
    fmt.Println(p4)
}

Output

{{Alice 30}
{Bob 25}
{Charlie 40}
{Diana 22}}

Common Pitfalls

Common mistakes when initializing structs include:

• Omitting field names in struct literals can cause errors if the struct changes.
• Using new returns a pointer, so dereference is needed to access values.
• Not initializing fields leaves them with zero values, which might be unexpected.

go

package main

import "fmt"

type Person struct {
    Name string
    Age  int
}

func main() {
    // Wrong: omitting field names can be unclear
    // p := Person{"Eve"} // Error: missing Age field

    // Correct: use field names
    p := Person{Name: "Eve", Age: 28}

    // Using new returns pointer
    pPtr := new(Person)
    // Wrong: printing pointer directly
    fmt.Println(pPtr) // prints address
    // Correct: dereference pointer
    fmt.Println(*pPtr) // prints zero values
}

Output

&{ 0}
{ 0}

Quick Reference

Method	Description	Example
Struct literal with field names	Clear and safe way to initialize	p := Person{Name: "Alice", Age: 30}
Struct literal without field names	Less clear, order-dependent	p := Person{"Bob", 25}
Using new keyword	Creates pointer with zero values	p := new(Person)
Declare variable and assign fields	Initialize fields later	var p Person; p.Name = "Diana"

Key Takeaways

Use struct literals with field names for clear and safe initialization.

The new keyword returns a pointer to a struct with zero values.

Avoid omitting field names to prevent errors when struct fields change.

You can declare a struct variable and assign fields later.

Dereference pointers returned by new to access struct values.