实现一个CURL

使用方法1：

`	//以下设置不不要的可以不设置
 	curl := New() //创建对象
 	curl.SetMethod("GET") //设置请求方法
 	curl.SetUrl("https://www.baidu.com/") //设置Url
 	curl.SetHeader("Content-Type","application/json") //设置请求类型
 	curl.SetBody("")//设置请求体，
 	curl.AddHeader("test","test01")//增加请求头test的值
 	curl.AddHeader("test","test02")//增加请求头
 	err := curl.Do()`

curl请求的详细信息

`{"method":"GET","url":"https://xxx.test.com/","status":200,"delay":321,"request":{"Header":{"Content-Type":["application/json"],"Test":["test01","test02"]},"Body":"","ContentType":"application/json","ContentLength":0},"response":{"Header":{"Connection":["keep-alive"],"Content-Length":["8"],"Content-Type":["text/html; charset=utf-8"],"Date":["Thu, 28 Jun 2018 04:21:12 GMT"],"Server":["nginx"]},"Body":"shop api","ContentType":"text/html; charset=utf-8","ContentLength":8}}

`

使用方法2(推荐)：

`	//curl也可以通过链式构建,
 	cb := &CurlBuilder{}
 	curl :=cb.SetMethod("GET").SetUrl("https://www.baidu.com/").SetHeader("Content-Type","application/json").Build()
 	//执行请求
 	err := curl.Do()`