Get did from metadata instead with _tmp_hack.

cmd/goic/main.go

@@ -140,8 +140,11 @@ func fetchDID(canisterId principal.Principal) ([]byte, error) {
 		return nil, err
 	}
 	var did string
+	// This endpoint has been deprecated and removed starting with moc v0.11.0.
 	if err := a.Query(canisterId, "__get_candid_interface_tmp_hack", nil, []any{&did}); err != nil {
-		return nil, err
+		// It is recommended for the canister to have a custom section called "icp:public candid:service", which
+		// contains the UTF-8 encoding of the Candid interface for the canister.
+		return a.GetCanisterMetadata(canisterId, "candid:service")
 	}
 	return []byte(did), nil
 }

ic/ic_test.go

@@ -81,6 +81,20 @@ func TestModules(t *testing.T) {
 		if err := a.Authorize(principal.AnonymousID); err != nil {
 			t.Fatal(err)
 		}
+
+		{
+			a, err := agent.New(config)
+			if err != nil {
+				t.Fatal(err)
+			}
+			did, err := a.GetCanisterMetadata(cId, "candid:service")
+			if err != nil {
+				t.Fatal(err)
+			}
+			if len(did) == 0 {
+				t.Error("empty did")
+			}
+		}
 	})
 
 	t.Run("management canister", func(t *testing.T) {