Structs

Structs

A struct groups related fields under one named type — the closest thing Go has to a class, minus inheritance:

type Person struct {
	Name string
	Age  int
}
 
p := Person{Name: "Haleh", Age: 34}
fmt.Println(p.Name) // Haleh
 
p.Age = 35 // structs are mutable by default

Capitalized field names (Name, Age) are exported outside the package, same rule as everywhere else in Go — lowercase them (name, age) if a field should stay package-private.

Structs are values, not references

This is the detail most likely to surprise you coming from Python or JavaScript, where assigning or passing an object just copies a reference to the same underlying data. In Go, assigning a struct — or passing one to a function — copies the whole thing:

p1 := Person{Name: "Ada", Age: 36}
p2 := p1
p2.Name = "Grace"
 
fmt.Println(p1.Name) // Ada — unchanged
fmt.Println(p2.Name) // Grace

p2 is an independent copy; modifying it never touches p1. This is exactly the kind of behavior that will bite you once — pass a struct to a function expecting to mutate the caller's copy, and watch the caller's copy stay unchanged — before it clicks. The fix, once you need it, is a pointer to the struct instead of the struct itself, which you'll see properly in the next module.

Nested structs

type Address struct {
	City    string
	Country string
}
 
type Person struct {
	Name    string
	Age     int
	Address Address
}
 
p := Person{
	Name: "Haleh",
	Age:  34,
	Address: Address{
		City:    "Toronto",
		Country: "Canada",
	},
}
 
fmt.Println(p.Address.City) // Toronto

Composing small structs like this — rather than one large flat one — is the idiomatic way to model related-but-distinct groups of fields, and it sets up naturally for the methods and interfaces you'll meet next.