How to replicate do while in go?

Question

I want a set of code to be executed until user explicitly wants to exit the function. For eg: when a user runs the program, he will see 2 options:

1. Run again
2. Exit

this will be achieved using switch case structure. Here if user presses 1, set of functions associated with 1 will execute and if user presses 2, the program will exit. How should i achieve this scenario in golang ? In java, i believe this could be done using do while structure but go doesn't support do while loop. Following is my code which i tried but this goes in a infinite loop:

func sample() {     var i = 1     for i > 0 {         fmt.Println("Press 1 to run")         fmt.Println("Press 2 to exit")         var input string         inpt, _ := fmt.Scanln(&input)         switch inpt {         case 1:             fmt.Println("hi")         case 2:             os.Exit(2)         default:             fmt.Println("def")         }     } } 

The program irrespective of the input, prints only "hi". Could someone please correct me what wrong i am doing here ?

Thanks.

Answer 1

A do..while can more directly be emulated in Go with a for loop using a bool loop variable seeded with true.

for ok := true; ok; ok = EXPR { } 

is more or less directly equivalent to

do { } while(EXPR) 

So in your case:

var input int for ok := true; ok; ok = (input != 2) {     n, err := fmt.Scanln(&input)     if n < 1 || err != nil {         fmt.Println("invalid input")         break     }      switch input {     case 1:         fmt.Println("hi")     case 2:         // Do nothing (we want to exit the loop)         // In a real program this could be cleanup     default:         fmt.Println("def")     } } 

Edit: Playground (with a dummied-out Stdin)

Though, admittedly, in this case it's probably overall clearer to just explicitly call (labelled) break, return, or os.Exit in the loop.