Go Constants

The keyword for Golang Constant is const , Once the Constant variable declared it cannot be modified.

Same as Var keyword, we can declare constant as two types.
    1. Typed      --  const  a string = "abc" 
    2. Untyped --  const  a ="abc" 

Example for using Golang Constants:

package main
import "fmt"
// declaring Multiple variables
const (
	a = 1
	b = "hi"
	c = 1.1
)
func main() {
	fmt.Println(a)
	fmt.Println(b)
	fmt.Println(c)
}

Output:

1
hi
1.1

Another Example:

package main
import "fmt"
func main() {
	const a = "Hello"
	a = "Hi"
	fmt.Println(a)
}

Output:

./prog.go:7:2: cannot assign to a (untyped string constant "Hello")
Go build failed.

Another Example:

package main
import "fmt"
func main() {

	// declare and initialize a constant string
	const s string = "MY_CONST"

	// define a custom string type - str
	type str string

	// storing the const variable in a new variable is allowed
	var newString string = s

	// storing the const variable in a new custom type variable is allowed
	var customString str = s

	// But storing the custom type variable in the normal string variable is not allowed
	newString = customString

	fmt.Println(newString)
	fmt.Println(customString)
}

Output:
./prog.go:17:25: cannot use s (constant "MY_CONST" of type string) as str value in variable declaration
./prog.go:20:14: cannot use customString (variable of type str) as string value in assignment
Go build failed.