go 29 lines · 5 steps

How a www-to-apex redirect middleware works in Gin

A Gin middleware that permanently redirects www hostnames to their apex domain while preserving scheme and path.

Explained by highlit
Gin Intermediate middleware http-redirect closures url-handling
1package middleware
2 
3import (
4 "net/http"
5 "strings"
6 
7 "github.com/gin-gonic/gin"
8)
9 
10func RedirectWWW() gin.HandlerFunc {
11 return func(c *gin.Context) {
12 host := c.Request.Host
13 if !strings.HasPrefix(host, "www.") {
14 c.Next()
15 return
16 }
17 
18 apex := strings.TrimPrefix(host, "www.")
19 
20 scheme := "http"
21 if c.Request.TLS != nil || c.GetHeader("X-Forwarded-Proto") == "https" {
22 scheme = "https"
23 }
24 
25 target := scheme + "://" + apex + c.Request.URL.RequestURI()
26 c.Redirect(http.StatusMovedPermanently, target)
27 c.Abort()
28 }
29}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Returning a closure that captures nothing lets a middleware factory produce a reusable handler.
  2. 2Detecting HTTPS behind a proxy means checking X-Forwarded-Proto, not just the raw TLS connection.
  3. 3A 301 with the original RequestURI keeps the visitor's path and query intact across the redirect.

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