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// Copyright 2020 the oak authors. All rights reserved. MIT license.
import { Middleware } from "../deps.ts";
/** A middleware that will set the response time for other middleware in * milliseconds as `X-Response-Time` which can be used for diagnostics and other * instrumentation of an application.  Utilise the middleware before the "real" * processing occurs. *  * ```ts * import { responseTimeHeader } from "https://deno.land/x/oak-middleware/mod.ts"; * import { Application } from "https://deno.land/x/oak/mod.ts" *  * const app = new App(); * app.use(responseTimeHeader); *  * // other middleware *  * await app.listen(":80"); * ``` */export const responseTypeHeader: Middleware = async function (ctx, next) {  const start = Date.now();  await next();  const ms = Date.now() - start;  ctx.response.headers.set("X-Response-Time", `${ms}ms`);};