If with a short statement

Like for, the if statement can start with a short statement to execute before the condition.

Variables declared by the statement are only in scope until the end of the if.

(Try using v in the last return statement.)

if-with-a-short-statement.go

package main
import (
    "fmt"
    "math"
)
func pow(x, n, lim float64) float64 {
    if v := math.Pow(x, n); v < lim {
        return v
    }
    return lim
}
func main() {
    fmt.Println(
        pow(3, 2, 10),
        pow(3, 3, 20),
    )
}