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Example of using context.Value() as a middleware chain
package goexperiments
import (
type HandlerMiddleware interface {
HandleHTTPC(ctx context.Context, rw http.ResponseWriter, req *http.Request, next http.Handler)
var function1 HandlerMiddleware = nil
var function2 HandlerMiddleware = nil
func addUserID(rw http.ResponseWriter, req *http.Request, next http.Handler) {
ctx := context.WithValue(req.Context(), "userid", req.Header.Get("userid"))
req = req.WithContext(ctx)
next.ServeHTTP(rw, req)
func useUserID(rw http.ResponseWriter, req *http.Request, next http.Handler) {
uid := req.Context().Value("userid")
func makeChain(chain ...HandlerMiddleware) http.Handler {return nil}
type Server struct {}
func (s *Server) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
req = req.WithContext(context.Background())
chain := makeChain(addUserID, function1, function2, useUserID)
chain.ServeHTTP(rw, req)

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@gaorong gaorong commented Apr 21, 2018

req = req.WithContext(context.Background()) need't set the request's initial context explicitly, cause default is context.Background().

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