package main                                                 

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

func fetch_url(url string, responses *chan string) {
  log.Println("Fetching ", url)
  response, err := http.Get(url)
  log.Println("Finish fetching ", url, response.Status)    
  if err != nil {
    *responses <- "Failed"                               
  } else {
    *responses <- response.Status                        
  }                                                        
}                                                            

func handler(w http.ResponseWriter, r *http.Request) {       
  urls := []string{
    "https://google.com",
    "https://www.facebook.com",                          
    "https://www.ebay.co.uk",                            
  }                                                        
    
  // trigger requests
  responses := make(chan string, len(urls))                
  for _, url := range urls {
    go fetch_url(url, &responses)                        
  }                                                        
    
  // collect responses
  statuses := make([]string, len(urls))                    
  for i := 0; i < len(statuses); i++ {                     
      statuses[i] = <-responses                            
  }
  close(responses)                                         

  responseText, _ := json.Marshal(statuses)                
  
  fmt.Fprintf(w, string(responseText))                     
}                                                            

func main() {
  http.HandleFunc("/", handler)
  http.ListenAndServe(":8000", nil)                        
}