goproxy: add goproxy to AppManager and use it in CI via flake.nix

Change-Id: I489d202c34219434653cfe3afbb19937dadd204e
diff --git a/flake.nix b/flake.nix
index 5a108db..4ca91c3 100644
--- a/flake.nix
+++ b/flake.nix
@@ -52,6 +52,9 @@
 
           PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD = "1";
           PLAYWRIGHT_SKIP_VALIDATE_HOST_REQUIREMENTS = "true";
+
+          GOPROXY = "https://goproxy.v1.dodo.cloud";
+          GONOPROXY = "none";
         };
       }
     );