# File lib/faraday/connection.rb, line 215
    def run_request(method, url, body, headers)
      if !METHODS.include?(method)
        raise ArgumentError, "unknown http method: #{method}"
      end

      request = build_request(method) do |req|
        req.url(url)                if url
        req.headers.update(headers) if headers
        req.body = body             if body
        yield req if block_given?
      end

      env = request.to_env(self)
      self.app.call(env)
    end