intercept 
Middleware to easily intercept and/or modify HTTP requests/responses before sending them to the client/server.
Installation
go get -u gopkg.in/vinxi/intercept.v0API
See the godoc reference for detailed API documentation.
Examples
Response interceptor and modifier
package main
import (
"fmt"
"gopkg.in/vinxi/intercept.v0"
"gopkg.in/vinxi/vinxi.v0"
"strings"
)
func main() {
fmt.Printf("Server listening on port: %d\n", 3100)
vs := vinxi.NewServer(vinxi.ServerOptions{Host: "localhost", Port: 3100})
// Intercept request and modify URI path
vs.Use(intercept.Request(func(req *intercept.RequestModifier) {
req.Request.RequestURI = "/html"
}))
// Intercept and replace response body
vs.Use(intercept.Response(func(res *intercept.ResponseModifier) {
data, _ := res.ReadString()
str := strings.Replace(data, "Herman Melville - Moby-Dick", "A Long History", 1)
res.String(str)
}))
vs.Forward("http://httpbin.org")
err := vs.Listen()
if err != nil {
fmt.Errorf("Error: %s\n", err)
}
}