constant in Go

Constants are declared like variables, but with the const keyword. 
Constants cannot be declared using the := syntax. 
Numeric constants are high-precision values. 
```
package main

import "fmt"

const s string = "constant"

func main() {
	const n = 500000000
	fmt.Println(s)
	fmt.Println(n)
}
```
An untyped constant takes the type needed by its context.
An int can store at maximum a 64-bit integer, and sometimes less.