Documentation
¶
Overview ¶
Package expires provides express middleware that sets an HTTP Expires header a fixed duration into the future. It fills the same role as the Node "express-expires" style helpers and the Expires option of static-file middleware such as serve-static: a relative freshness lifetime expressed as a duration is turned into an absolute HTTP-date on every response.
Use this middleware to give responses a coarse cache lifetime for HTTP/1.0 caches and proxies that predate Cache-Control, or simply as a belt-and-braces companion to Cache-Control: max-age. It is well suited to content that should be considered fresh for a fixed window after it is served — semi-static pages, infrequently changing JSON, downloadable assets. Mount it with app.Use over the routes whose responses should carry an expiry.
The handler runs anywhere in the chain and writes exactly one header. On each request it computes now().Add(Duration).UTC(), formats it with http.TimeFormat (the RFC 1123 GMT form required for HTTP dates), calls res.Set("Expires", value), and then invokes next() unconditionally. It never reads the request, never short-circuits, and does not touch the status or body; the header is set before next() so it is present when a downstream handler flushes the response. Unlike a header value computed once at construction time, the Expires timestamp is evaluated per request, so it always reflects the moment each request is handled plus the configured offset.
Behavior is governed by Options.Duration, which is added to the current time. A zero Duration (the zero-value Options) produces an Expires equal to the current time — effectively "expires immediately" — while a negative Duration yields a date in the past, marking the response already stale. The package uses an internal, overridable now function (defaulting to time.Now) so tests can pin the clock; production callers never interact with it. No upper bound is imposed on the duration, and the value is always emitted in UTC/GMT as the HTTP-date spec requires.
Regarding parity with the Node original: the semantics match the common Express pattern of translating a relative max-age-like duration into an absolute Expires header formatted as an HTTP date. The differences are that this port sets only the Expires header and does not also emit Cache-Control (callers who want both should pair it with a cache-control middleware), and that it takes a Go time.Duration rather than a milliseconds number or a date string. It performs no conditional-request or freshness checking; it only stamps the header.
Example ¶
Example demonstrates stamping responses with an Expires header a fixed duration into the future. It builds an express app and mounts expires.New with an Options value giving a one-hour lifetime, then registers a route and drives a request through the app with net/http/httptest. The emitted Expires header is parsed back with http.ParseTime and compared against the request time to confirm it lies in the future. No Output comment is used because the header carries the wall-clock moment of the request and is therefore not deterministic; the example instead prints only a stable boolean.
package main
import (
"fmt"
"net/http"
"net/http/httptest"
"time"
"github.com/malcolmston/express"
"github.com/malcolmston/express/middleware/expires"
)
func main() {
app := express.New()
app.Use(expires.New(expires.Options{Duration: time.Hour}))
app.Get("/", func(req *express.Request, res *express.Response, next express.Next) {
res.Send("ok")
})
rec := httptest.NewRecorder()
app.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/", nil))
exp, err := http.ParseTime(rec.Header().Get("Expires"))
fmt.Println(err == nil && exp.After(time.Now()))
}
Output: true
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Source Files