Help with GR issue

.github/workflows/docs.yml

@@ -7,6 +7,12 @@ on:
     tags: '*'
   pull_request:
 
+concurrency:
+  # Skip intermediate builds: always.
+  # Cancel intermediate builds: only if it is a pull request build.
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -19,6 +25,7 @@ jobs:
         run: julia --project=docs/ -e 'using Pkg; Pkg.develop(PackageSpec(path=pwd())); Pkg.instantiate()'
       - name: Build and deploy
         env:
+          GKSwstype: nul # turn off GR's interactive plotting for notebooks
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} # For authentication with GitHub Actions token
           DOCUMENTER_KEY: ${{ secrets.DOCUMENTER_KEY }} # For authentication with SSH deploy key
         run: julia --project=docs/ docs/make.jl