Add error to GetSession return values

- Add button to copy instance SSH access

handlers/close_session.go

@@ -5,16 +5,20 @@ import (
 	"net/http"
 
 	"github.com/gorilla/mux"
+	"github.com/play-with-docker/play-with-docker/storage"
 )
 
 func CloseSession(rw http.ResponseWriter, req *http.Request) {
 	vars := mux.Vars(req)
 	sessionId := vars["sessionId"]
 
-	session := core.SessionGet(sessionId)
-	if session == nil {
+	session, err := core.SessionGet(sessionId)
+	if err == storage.NotFoundError {
 		rw.WriteHeader(http.StatusNotFound)
 		return
+	} else if err != nil {
+		rw.WriteHeader(http.StatusInternalServerError)
+		return
 	}
 
 	if err := core.SessionClose(session); err != nil {