此示例将展示如何在 Go 中创建基本的日志记录中间件。
中间件只需将 http.HandlerFunc 作为其参数之一，将其包装起来并返回一个新的 http.HandlerFunc 供服务器调用。
// basic-middleware.go
package main
import (
"fmt"
"log"
"net/http"
)
func logging(f http.HandlerFunc) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
log.Println(r.URL.Path)
f(w, r)
}
}
func foo(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, "foo")
}
func bar(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, "bar")
}
func main() {
http.HandleFunc("/foo", logging(foo))
http.HandleFunc("/bar", logging(bar))
http.ListenAndServe(":8080", nil)
}$ go run basic-middleware.go
2017/02/10 23:59:34 /foo
2017/02/10 23:59:35 /bar
2017/02/10 23:59:36 /foo?bar
$ curl -s http://localhost:8080/foo
$ curl -s http://localhost:8080/bar
$ curl -s http://localhost:8080/foo?bar