Install Rust toolchain

Author: sourcefrog

.github/workflows/codebuild.yml

@@ -10,6 +10,10 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v2
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: beta
+      - uses: Swatinem/rust-cache@v2
       - run: cargo rustc --version
       - run: rustup toolchain list
       - run: cargo install cargo-nextest