Middleware

• Introduction
• Writing Middleware
  • Middleware With Services
  • The Order It Runs In
  • App-Wide Middleware
• Choosing a Guard or Middleware
• Middleware and Live Sessions
• Middleware and Decorators

Introduction

Middleware is ordinary Go logic around HTTP. You reach for it for concerns that belong to the request and response rather than to a page: headers, logging, compression and rate limits.

It lives in the page tree beside the pages it wraps, or is passed to the app for every request.

Writing Middleware

Put subtree middleware in pages/middleware.go, or in a descendant folder's middleware.go. This one logs each request before passing it on:

package pages

import (
    "log"
    "net/http"
)

func Middleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        log.Printf("%s %s", r.Method, r.URL.Path)
        next.ServeHTTP(w, r)
    })
}

Not calling next short-circuits the request.

Middleware With Services

A constructor form can receive services and return web.Middleware. See Dependency Injection.

The Order It Runs In

Root middleware wraps child middleware. Guards and layout loading then run before binding, mount and handlers.

App-Wide Middleware

App-wide middleware can be passed as web.Use(mw) to web.New(pages.Routes(), …).

Choosing a Guard or Middleware

Use a folder's Guard.Load for typed resource and permission checks that return a web error; see Guards. Use middleware for HTTP concerns such as headers, logging, compression and rate limits.

Middleware and Live Sessions

HTTP middleware wraps the initial request and the socket join, not every event on an established socket. Protected event handlers must authorize actions with the current identity.

WARNING

Do not infer ongoing permission from a successful join.

Middleware and Decorators

Language-level call decorators still apply to logic functions and handlers. They see typed arguments and results; HTTP middleware sees the request and response. Choose the layer that owns the check. See Decorators.