Build a chain of http.HandlerFuncs in go

handlerChain.go

package httpServer

import (
	"net/http"
)

/*
GIVEN MIDDLEWARES TO WIRE IN COMPONENTS LIKE:
func RequestIDMiddleware(makeTimeBasedUUIDFn func() string, next http.HandlerFunc) http.HandlerFunc {
	fn := func(w http.ResponseWriter, r *http.Request) {
		ctx := r.Context()

		requestID := makeTimeBasedUUIDFn()
		ctx = context.WithValue(ctx, ContextKeyRequestID, requestID)
		w.Header().Set("Request-ID", requestID)

		next(w, r.WithContext(ctx))
	}

	return http.HandlerFunc(fn)
}

EXAMPLE
	handler := (&HandlerChain{}).
		Do(func(chain http.HandlerFunc) http.HandlerFunc {
			return RequestIDMiddleware(t.makeTimeBasedUUIDFn, chain)
		}).
		Do(func(chain http.HandlerFunc) http.HandlerFunc {
			return ParamsMiddleware(chain)
		}).
		Finally(router)
*/

type HandlerChain struct {
	handlerFns []func(next http.HandlerFunc) http.HandlerFunc
}

func (t *HandlerChain) Do(fn func(next http.HandlerFunc) http.HandlerFunc) *HandlerChain {
	t.handlerFns = append(t.handlerFns, fn)
	return t
}

func (t *HandlerChain) Finally(handler http.Handler) http.Handler {
	h := handler.ServeHTTP
	for i := len(t.handlerFns) - 1; i >= 0; i -= 1 {
		h = t.handlerFns[i](h)
	}
	return http.HandlerFunc(h)
}