Middleware

Trailing Slash

Remove or add the trailing slash on request paths, or redirect clients to one form.

Trailing Slash makes /users/ and /users reach the same route, or sends clients to one canonical form of each URL. Zinc already matches both forms unless you turn on StrictRouting, so you’d add this to a strict app, or when you want one URL per page for caches and search engines.

Usage

import "github.com/0mjs/zinc/middleware/trailingslash"

app := zinc.New(zinc.Config{StrictRouting: true})
app.Use(trailingslash.New())

app.Get("/users", func(c *zinc.Context) error {
  return c.String("users at " + c.Path())
})

curl http://localhost:8080/users/    # users at /users
curl http://localhost:8080/users//   # users at /users

Without the middleware, the strict app answers /users/ with a 404. The slash is removed before routing, and the client isn’t told.

In a group, routing has already chosen a handler by the time trailingslash runs, so changing the path can’t change the route. Registering it on a group panics at startup, in every mode:

app.Group("/api").Use(trailingslash.New())
// panic: zinc: trailingslash middleware on group "/api" would run after routing, where it can't work; register it with app.Use, or app.UsePrefix("/api", ...) for the group's paths

On a single route it can’t change the route either, and logs a warning through slog the first time it runs.

Defaults

Setting	Default
Direction	remove trailing slashes
Client sees	nothing: the path is changed before routing
Redirect status	`301 Moved Permanently` (when `Redirect` is on)

Configuration

Redirect clients to the form without the slash, keeping the method and body:

app.Use(trailingslash.New(trailingslash.Config{
  Redirect:   true,
  StatusCode: zinc.StatusPermanentRedirect,
}))

curl -i "http://localhost:8080/users/?page=2"
# HTTP/1.1 308 Permanent Redirect
# Location: /users?page=2

Field	Default	Meaning
`Add`	`false`	Adds a trailing slash instead of removing it
`Redirect`	`false`	Redirects the client to the changed path instead of routing it directly. The query string is kept, the path keeps its escaping, and the target always stays on this site.
`StatusCode`	`301`	Redirect status when `Redirect` is on. A value outside `3xx` sends `302 Found`.

Always end with a slash

For sites whose URLs end in /, add the slash and redirect to it:

app := zinc.New(zinc.Config{StrictRouting: true})
app.Use(trailingslash.New(trailingslash.Config{Add: true, Redirect: true}))

app.Get("/docs/", func(c *zinc.Context) error {
  return c.String("docs")
})

curl -i http://localhost:8080/docs
# HTTP/1.1 301 Moved Permanently

The root path / is always left alone.

Static folders

A folder served by Static or StaticFS lives at its URL with a trailing slash, and redirects there without one. When removing slashes, Trailing Slash leaves a folder’s URL alone, so the two never redirect back and forth. Files under a static mount are treated like any other path.

Errors

trailingslash never fails a request. If the changed path has no route, the client gets the usual 404.

trailingslash.New panics at startup when it’s given more than one Config.

Routing: how Zinc treats trailing slashes, and StrictRouting.
Redirect: redirects old paths to new ones.
Rewrite: routes one path as another.