Libcurl：无法向requestbin发送自定义标头？

Question

这是代码

#include <curl/curl.h>

int main(){
   CURL * curl;
   curl=curl_easy_init();
   struct curl_slist *headers=NULL;
   headers = curl_slist_append(headers, "Connection: keep-alive");
   headers = curl_slist_append(headers,"a : b");
   curl_easy_setopt(curl,CURLOPT_URL,"requestb.in/1ar78su1");
   curl_easy_setopt(curl,CURLOPT_HTTPHEADER,headers);
   curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
   curl_easy_perform(curl);
   curl_slist_free_all(headers);
  }

继承请求链接： 为什么它没有显示＆＃34; a：b＆＃34;和＆＃34;连接：保持活力＆＃34;在requestbin？