Tiny Go web server to multiply two integers

multiply.go

package main

import (
	"fmt"
	"net/http"
	"strconv"
)

func main() {
	http.HandleFunc("/multiply", func(w http.ResponseWriter, r *http.Request) {
		query := r.URL.Query()
		a, err := strconv.Atoi(query.Get("a"))
		if err != nil {
			http.Error(w, "'a' invalid", http.StatusBadRequest)
			return
		}
		b, err := strconv.Atoi(query.Get("b"))
		if err != nil {
			http.Error(w, "'b' invalid", http.StatusBadRequest)
			return
		}
		result := a * b
		fmt.Fprintf(w, "%d\n", result)
	})
	fmt.Println("listening on http://localhost:8081")
	http.ListenAndServe(":8081", nil)
}