Do Go switch/cases fallthrough or not?

No, Go switch statements do not fall through automatically. 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