Declaring a Constant in Go

A constant is a name for a value that will not change while the program runs. You can declare it with const. Unlike a variable, you cannot give that name a new value later. in The Golang Official Documentation

package main
 
import "fmt"
 
func main() {
	const maxItems = 30_000
	fmt.Println(maxItems)
}

If you’ll run this, you’ll get 30000

const maxItems = 30_000 gives the fixed value a readable name. The underscore in the number is only for readability, so printing it shows 30000.

Try assigning a new value to the constant:

package main
 
import "fmt"
 
func main() {
	const maxItems = 30_000
	maxItems = 100 // Intentional error.
	fmt.Println(maxItems)
}

You’ll get a compilation error