Fix This Code

description.md

This bit of code fetches 100 integers from an endpoint called https://example.com/integers which returns { "value": 2 } . The code makes 10 concurrent requests to the endpoint so we don't trigger a rate limit and then reports a list of which integers were even and which were odd.

How would you improve the following code? Feel free to rewrite as if this was production code. There are coding mistake and often just bad form in the code, please fix it!

main.go

func main() {  
   s := make(chan bool, 10)  
   var result map[string][]int  
  
   for i := 0; i <= 100; i++ {  
      s <- true  
      go func() {  
         // /integers endpoint returns `{ "value": 2 }`  
         resp, err := http.Get("<https://"> + domain + "/integers/" + fmt.Sprint(i)))  
         if err != nil {  
            panic(err)  
         }  
  
         var p map[string]interface{}  
         err := json.Unmarshal(resp.Body, &p)  
         if err == nil {  
            panic(err)  
         }  
  
         if isEven(p["value"].(int)) {  
            result["even"] = append(result["even"], p["value"].(int))  
         } else {  
            result["odd"] = append(result["odd"], p["value"].(int))  
         }  
         <-s  
      }()  
   }  
   // TODO: Print out `result`  
}

func isEven(input int) bool {
	switch input {
	case 0:
		return true
	case 1:
		return false
	default:
		return isEven(input - 2)
	}
}

server.go

// This is the endpoint which returns the integers for the fix this code challenge
package main

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

type Response struct {
	Value int `json:"value"`
}

type Error struct {
	Message string `json:"error"`
}

func main() {
	handler := func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")

		num, err := strconv.Atoi(r.URL.Path)
		if err != nil {
			w.WriteHeader(http.StatusBadRequest)
			_ = json.NewEncoder(w).Encode(Error{Message: fmt.Sprintf("invalid input: %s", r.URL.Path)})
			return
		}

		err = json.NewEncoder(w).Encode(Response{Value: num})
		if err != nil {
			http.Error(w, "while marshalling", http.StatusInternalServerError)
			return
		}
	}

	http.Handle("/integers/", http.StripPrefix("/integers/", http.HandlerFunc(handler)))

	fmt.Printf("Listening on :8080...\n")
	if err := http.ListenAndServe(":8080", nil); err != nil {
		fmt.Println("Error starting the server:", err)
	}
}