if/else, switch, the lone for loop, break, continue.

switch and Type Switch

Go's switch is safer than C's — no fallthrough by default, no need for break. It also doubles as a way to inspect a value's runtime type.

Value switch

A case can list multiple values separated by commas. Order doesn't matter — the first match wins.

No fallthrough — but you can opt in

switch n {
case 1:
    fmt.Println("one")
    fallthrough
case 2:
    fmt.Println("two or one")
}

fallthrough jumps to the next case body, ignoring its condition. Use sparingly.

Switch with no condition

A switch without an expression is a cleaner if / else if chain:

switch {
case n < 0:
    fmt.Println("negative")
case n == 0:
    fmt.Println("zero")
default:
    fmt.Println("positive")
}

Switch with init

Like if, you can declare a variable in the switch line:

switch tag := getTag(); tag {
case "v1":
    ...
}

Type switch

Use switch v := x.(type) to ask "what is x?" — common with interface{} / any values. The variable v is rebound to the matched type inside each case.

We come back to type assertions properly in chapter 12.