add example for serve file

example/httpserver/serve_file/main.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"net/http"
+	"os"
+	"strings"
+
+	"github.com/gogf/gf/v2/frame/g"
+	"github.com/gogf/gf/v2/net/ghttp"
+)
+
+var pathMap = map[string]string{
+	"/aaa/": "./",
+}
+
+// ServeFile serves the file to the response.
+func ServeFile(r *ghttp.Request) {
+	truePath := r.URL.Path
+	// Replace the path prefix.
+	for k, v := range pathMap {
+		if strings.HasPrefix(truePath, k) {
+			truePath = strings.Replace(truePath, k, v, 1)
+			break
+		}
+	}
+
+	// Use file from dist.
+	file, err := os.Open(truePath)
+	if err != nil {
+		r.Response.WriteStatus(http.StatusForbidden)
+		return
+	}
+	defer file.Close()
+
+	// Clear the response buffer before file serving.
+	// It ignores all custom buffer content and uses the file content.
+	r.Response.ClearBuffer()
+
+	info, _ := file.Stat()
+	if info.IsDir() {
+		r.Response.WriteStatus(http.StatusForbidden)
+	} else {
+		r.Response.ServeContent(info.Name(), info.ModTime(), file)
+	}
+}
+
+func main() {
+	s := g.Server()
+	s.Use(ghttp.MiddlewareHandlerResponse)
+	s.BindHandler("/*", ServeFile)
+	s.SetPort(8080)
+	s.Run()
+}
+
+// http://127.0.0.1:8080/aaa/main.go