use github to fetch packages (#166)

Author: piever

.github/workflows/ci.yml

@@ -34,6 +34,7 @@ jobs:
             ${{ runner.os }}-test-
             ${{ runner.os }}-
       - run: julia --project=@. -e '
+            ENV["JULIA_PKG_SERVER"] = "";
             using Pkg;
             Pkg.build();
             Pkg.test(coverage=true)'