fix(vhost): match virtual host names case-insensitively

vhost.go

@@ -3,14 +3,25 @@
 
 package echo
 
-import "net/http"
+import (
+	"net/http"
+	"strings"
+)
 
 // NewVirtualHostHandler creates instance of Echo that routes requests to given virtual hosts
 // when hosts in request does not exist in given map the request is served by returned Echo instance.
+//
+// Host names are matched case-insensitively (RFC 9110 Section 4.2.3), so a request with
+// `Host: Example.com` reaches the instance registered as `example.com`. The map is copied,
+// later changes to it have no effect.
 func NewVirtualHostHandler(vhosts map[string]*Echo) *Echo {
 	e := New()
+	hosts := make(map[string]*Echo, len(vhosts))
+	for host, vhost := range vhosts {
+		hosts[strings.ToLower(host)] = vhost
+	}
 	e.serveHTTPFunc = func(w http.ResponseWriter, r *http.Request) {
-		if vh, ok := vhosts[r.Host]; ok {
+		if vh, ok := hosts[strings.ToLower(r.Host)]; ok {
 			vh.ServeHTTP(w, r)
 			return
 		}

vhost_test.go

@@ -72,6 +72,13 @@ func TestVirtualHostHandler(t *testing.T) {
 			expectBody:   http.StatusText(http.StatusOK),
 			expectStatus: http.StatusOK,
 		},
+		{
+			name:         "OK Host Root, host in different case",
+			whenHost:     "OK.Com",
+			whenPath:     "/",
+			expectBody:   http.StatusText(http.StatusOK),
+			expectStatus: http.StatusOK,
+		},
 		{
 			name:         "Teapot Host Root",
 			whenHost:     "teapot.com",