def http_headers
      env.select { |k, _v| (k.start_with?("HTTP_") && k != "HTTP_VERSION") || k == "CONTENT_TYPE" }
        .collect { |k, v| [k.sub(/^HTTP_/, ""), v] }
        .collect { |k, v| [k.split("_").collect(&:capitalize).join("-"), v] }
    end
def http_headers
      env.select { |k, _v| (k.start_with?("HTTP_") && k != "HTTP_VERSION") || k == "CONTENT_TYPE" }
        .collect { |k, v| [k.sub(/^HTTP_/, ""), v] }
        .collect { |k, v| [k.split("_").collect(&:capitalize).join("-"), v] }
    end
Get HTTP headers.

 @return [Hash]