Gorilla Cache-Control for static files

cache-control.go

// Source: https://stackoverflow.com/questions/48876324/gorilla-mux-golang-cache-static-files

package main

import (
    "associations"
    "html/template"
    "net/http"
    "log"
    "io/ioutil"

    "github.com/gorilla/mux"
    "github.com/rs/cors"
    "google.golang.org/appengine"
    "google.golang.org/appengine/mail"
)

var index = template.Must(template.ParseFiles(
    "dist/index.html",
))

func init() {
    r := mux.NewRouter()
    r.HandleFunc("/", homeHandler)  
    r.HandleFunc("/api/{tenant}/certificates", associations.GetCertificate).Methods("GET")
    r.HandleFunc("/api/{tenant}/requests", associations.PostRequest).Methods("POST")

    // handle static files
    r.PathPrefix("/static/").Handler(
        http.StripPrefix("/static/", http.FileServer(http.Dir("dist/static/"))))

    r.NotFoundHandler = http.HandlerFunc(homeHandler) // work around for SPA serving index.html

    handler := cors.Default().Handler(r)
    http.Handle("/", handler)
}

   // handle static files
        r.PathPrefix("/static/").Handler(http.StripPrefix("/static/", 
CacheControlWrapper(http.FileServer(http.Dir("dist/static/")))))

    ....

func CacheControlWrapper(h http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        w.Header().Set("Cache-Control", "max-age=2592000") // 30 days
        h.ServeHTTP(w, r)
    })
}