Move swappableMux and its methods to its own module

internal/server/user/server.go

@@ -2,29 +2,8 @@ package user
 
 import (
 	"net/http"
-	"sync"
-
-	"github.com/gorilla/mux"
 )
 
-type swappableMux struct {
-	m    sync.RWMutex
-	root mux.Router
-}
-
-func (sm *swappableMux) get() mux.Router {
-	sm.m.RLock()
-	defer sm.m.RUnlock()
-
-	return sm.root
-}
-
-func (sm *swappableMux) set(mux mux.Router) {
-	sm.m.Lock()
-	sm.root = mux
-	sm.m.Unlock()
-}
-
 var Server http.Server
 
 func Run() {