main.go

package main

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

func sendResponse(w http.ResponseWriter, r *http.Request) {
  keys, ok := r.URL.Query()["a"]
  if !ok || len(keys[0]) < 1 {
      log.Println("Url Param 'a' is missing")
      return
  }

  a, err := strconv.Atoi(keys[0])

  if err != nil {
    return
  }

  keys, ok = r.URL.Query()["b"]
  if !ok || len(keys[0]) < 1 {
      log.Println("Url Param 'b' is missing")
      return
  }
  b, err := strconv.Atoi(keys[0])
  if err != nil {
    log.Println("Bad number!")
    return
  }

  fmt.Fprintf(w, "%d + %d = %d", a, b, sum(a,b))
}

func main() {
    http.HandleFunc("/", sendResponse)
    log.Fatal(http.ListenAndServe(":7000", nil))
}

func sum (a, b int) int {
  t := b + a
  return t
}