switch, case, fallthrough, and default

The switch statement allows you to branch execution based on the state of a variable. It is similar to the switch statement in C and other languages.

There is no fallthrough by default. This means once the end of a case is reached, the code exits the switch statement completely unless an explicit fallthrough command is provided. A default case can be provided if none of the cases are matched.

You can put a statement in front of the variable to be switched, such as the if statement. This creates a variable whose scope is limited to the switch statement.

This example demonstrates two switch statements. The first one uses hardcoded values and includes a default case. The second switch statement uses an alternate syntax that allows for a statement in the first line:

package main

import (
   "fmt"
   "math/rand"
)

func main() {
   x := 42

   switch x {
   case 25:
      fmt.Println("X is 25")
   case 42:
      fmt.Println("X is the magical 42")
      // Fallthrough will continue to next case
      fallthrough
   case 100:
      fmt.Println("X is 100")
   case 1000:
      fmt.Println("X is 1000")
   default:
      fmt.Println("X is something else.")
   }

   // Like the if statement a statement
   // can be put in front of the switched variable
   switch r := rand.Int(); r {
   case r % 2:
      fmt.Println("Random number r is even.")
   default:
      fmt.Println("Random number r is odd.")
   }
   // r is no longer available after the switch statement
}