Tour of Go 2.0

If and else

A variable declared in an if short statement is available in else blocks too — it lives for the entire if/else chain.

This is useful for error handling and conditional logic where you want one variable in play without it escaping into the outer scope.

Note that both calls to pow return their results before fmt.Println in main runs.

main.go ▶ Run in Playground 
package main

import (
	"fmt"
	"math"
)

func pow(x, n, lim float64) float64 {
	if v := math.Pow(x, n); v < lim {
		return v
	} else {
		fmt.Printf("%g >= %g\n", v, lim)
	}
	// can't use v here, though
	return lim
}

func main() {
	fmt.Println(
		pow(3, 2, 10),
		pow(3, 3, 20),
	)
}