Do Go switch/cases fallthrough or not?

Question

What happens when you reach the end of a Go case, does it fall through to the next, or assume that most applications don't want to fall through?

Answer 1

No, Go switch statements do not fall through by default. If you do want it to fall through, you must explicitly use a fallthrough statement. From the spec:

In a case or default clause, the last non-empty statement may be a (possibly labeled) "fallthrough" statement to indicate that control should flow from the end of this clause to the first statement of the next clause. Otherwise control flows to the end of the "switch" statement. A "fallthrough" statement may appear as the last statement of all but the last clause of an expression switch.

For example (sorry, I could not for the life of me think of a real example):

switch 1 { case 1:     fmt.Println("I will print")     fallthrough case 0:     fmt.Println("I will also print") } 

Outputs:

I will print I will also print 

https://play.golang.org/p/va6R8Oj02z

Answer 2

Break is kept as a default but not fallthrough. If you want to get onto the next case for a match, you should explicitly mention fallthrough.

switch choice { case "optionone":     // some instructions      fallthrough // control will not come out from this case but will go to next case. case "optiontwo":    // some instructions  default:     return  }