private final Map<String, Collection<String>> toMap(final HttpHeaders headers) {
    final Map<String, Collection<String>> map = new HashMap<String, Collection<String>>();
    for (final String header : headers.keySet()) {
      map.put(header, headers.getHeaderStringValues(header));
    }
    return map;
  }
This module directs Feign's http requests to
<a href="https://developers.google.com/api-client-library/java/google-http-java-client/">Google
HTTP Client</a>.

<pre>
GitHub github = Feign.builder().client(new GoogleHttpCliest()).target(GitHub.class,
"https://api.github.com");
googlehttpclient/src/main/java/feign/googlehttpclient/GoogleHttpClient.java