Multiple "set-cookie" headers get merged into one

[bageren]

import { default as express } from "npm:express@4.18.2";

const app = express();
const port = 3000;

app.get("/", (req, res) => {
  res.header("set-cookie", ["test1=1; Path=/;", "test2=2; Path=/;"]);
  res.send("Hello World!");
});

When I open localhost:3000, I see set-cookie: test1=1; Path=/;,test2=2; Path=/; in the response headers. This causes only the first one (test1) to be set, while test2 is ignored.

The expected result would be 2 set-cookie headers in the response:

set-cookie: test1=1; Path=/;
set-cookie: test2=2; Path=/;

Doing the exact same thing using Node v18.17.0 produces the expected result.

Version: Deno 1.41.3