sveltekit routes not working when deployed to server - html

Question

Here's my svelte.config.js and I'm using adapter-static :
const config = {
kit: {
adapter: adapter({
// default options are shown
pages: '../backend/build',
assets: '../backend/build',
fallback: null,
precompress: false,
}),
alias: {},
appDir: '_app',
browser: {
hydrate: true,
router: true,
},
files: {
assets: 'static',
hooks: 'src/hooks',
lib: 'src/lib',
params: 'src/params',
routes: 'src/routes',
serviceWorker: 'src/service-worker',
template: 'src/app.html',
},
floc: false,
methodOverride: {
parameter: '_method',
allowed: [],
},
paths: {
assets: '',
base: '',
},
trailingSlash: 'always',
vite: {
server: {
proxy: {
'/api': 'http://localhost:5555',
},
},
},
},
preprocess: null,};
From the backend (Go lang) I'm serving build directory & index.html file. The homepage works fine but whenever I click on any route, it sends get request to the server instead of redirecting in the app itself.
Here's the go code to serve from backend:
router := gin.Default()
router.StaticFile("/", "./build/index.html")
router.StaticFS("/_app", http.Dir("build/_app"))
I have also tried with the following code:
router.NoRoute(func(c *gin.Context) {
path := c.Request.URL.Path
c.File("./build/index.html")
})
Note: Things work fine when I run npm run preview.

Answer 1

The adapter-static has two distinct modes of operation: SPA and prerendering. When there are several routes, both the npm run dev and npm run preview works as intended, but once built, the static routing falls to the web server, in your case, the Go framework, but the same happens with any other static server (I have tested also Nginx and Apache).
I found a workaround to avoid converting the site to a SPA: Installing a url rewrite mechanism as a middleware in order to add the .html extension that the static server is expecting in the compiled site. In my case, I used Go Fiber github.com/gofiber/rewrite/v2 and it worked as intended (the same behavior as when using npm run dev)
For Nginx static server the solution is the same url rewrite and it could be used as explained here: https://www.codesmite.com/article/clean-url-rewrites-using-nginx

Answer 2

The homepage works fine but whenever I click on any route, it sends get request to the server instead of redirecting in the app itself
SvelteKit users internal router, or $app/navigator for links only if it detects a link to be the same domain as the current page. Likely your web server is misconfigured and there is a mismatch of domain somewhere in
The web browser address bar
Web server configuration
However, the question do not contain these details and is thus unanswerable "why" and how to fix it.