https://www.cnblogs.com/chaselogs/p/9399526.html

    1. // 中间件
    2. func middleware() gin.HandlerFunc {
    3.     return func(c *gin.Context) {
    4.         t := time.Now()
    5.         c.Set("example", "123456")
    6.         // c.Next()后就执行真实的路由函数，路由执行完成之后接着走time.Since(t)
    7.         c.Next()
    9.         // 从time.Now()到目前为止过了多长时间
    10.         latency := time.Since(t)
    11.         log.Print("--", latency)
    13.         // gin设置响应头，设置跨域
    14.         c.Header("Access-Control-Allow-Origin", "*")
    15.         c.Header("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
    16.         c.Header("Access-Control-Allow-Headers", "Action, Module, X-PINGOTHER, Content-Type, Content-Disposition")
    18.         //设置中间件的响应头，路由的响应头可以在路由返回中设置，参考/ping
    19.         // c.Writer.WriteHeader(http.StatusMovedPermanently)
    20.         status := c.Writer.Status()
    21.         log.Println("==", status)
    22.     }
    23. }
    25. func middle(c *gin.Context) {
    26.     example := c.MustGet("example").(string)
    27.     log.Println(example)
    28. }
    30. func main() {
    31.     r := gin.Default()
    33.     //中间件，只有在中间件之后注册的路由才会走中间件
    34.     r.Use(middleware())
    35.     //http://localhost:8081/middle
    36.     r.GET("/middle", middle)
    38.     r.Run(":8081")
    39. }