gin web框架解决跨域问题

//使用中间件
router.Use(Cors())

func Cors() gin.HandlerFunc {
    return func(c *gin.Context) {
        method := c.Request.Method

        origin := c.Request.Header.Get("Origin")
        var headerKeys []string
        for k, _ := range c.Request.Header {
            headerKeys = append(headerKeys, k)
        }
        headerStr := strings.Join(headerKeys, ", ")
        if headerStr != "" {
            headerStr = fmt.Sprintf("access-control-allow-origin, access-control-allow-headers, %s", headerStr)
        } else {
            headerStr = "access-control-allow-origin, access-control-allow-headers"
        }
        if origin != "" {
            //下面的都是乱添加的-_-~
            // c.Writer.Header().Set("Access-Control-Allow-Origin", "*")
            c.Header("Access-Control-Allow-Origin", "*")
            c.Header("Access-Control-Allow-Headers", headerStr)
            c.Header("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
            // c.Header("Access-Control-Allow-Headers", "Authorization, Content-Length, X-CSRF-Token, Accept, Origin, Host, Connection, Accept-Encoding, Accept-Language,DNT, X-CustomHeader, Keep-Alive, User-Agent, X-Requested-With, If-Modified-Since, Cache-Control, Content-Type, Pragma")
            c.Header("Access-Control-Expose-Headers", "Content-Length, Access-Control-Allow-Origin, Access-Control-Allow-Headers, Content-Type")
            // c.Header("Access-Control-Max-Age", "172800")
            c.Header("Access-Control-Allow-Credentials", "true")
            c.Set("content-type", "application/json")
        }

        //放行所有OPTIONS方法
        if method == "OPTIONS" {
            c.JSON(http.StatusOK, "Options Request!")
        }

        c.Next()
    }
}