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package middleware
import (
"net/http"
"time"
)
// Unix epoch time
var epoch = time.Unix(0, 0).Format(time.RFC1123)
// Taken from https://github.com/mytrile/nocache
var noCacheHeaders = map[string]string{
"Expires": epoch,
"Cache-Control": "no-cache, private, max-age=0",
"Pragma": "no-cache",
"X-Accel-Expires": "0",
}
var etagHeaders = []string{
"ETag",
"If-Modified-Since",
"If-Match",
"If-None-Match",
"If-Range",
"If-Unmodified-Since",
}
// NoCache is a simple piece of middleware that sets a number of HTTP headers to prevent
// a router (or subrouter) from being cached by an upstream proxy and/or client.
//
// As per http://wiki.nginx.org/HttpProxyModule - NoCache sets:
// Expires: Thu, 01 Jan 1970 00:00:00 UTC
// Cache-Control: no-cache, private, max-age=0
// X-Accel-Expires: 0
// Pragma: no-cache (for HTTP/1.0 proxies/clients)
func NoCache(h http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
// Delete any ETag headers that may have been set
for _, v := range etagHeaders {
if r.Header.Get(v) != "" {
r.Header.Del(v)
}
}
// Set our NoCache headers
for k, v := range noCacheHeaders {
w.Header().Set(k, v)
}
h.ServeHTTP(w, r)
}
return http.HandlerFunc(fn)
}
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