change env syntax

.github/workflows/ci.yml

@@ -27,10 +27,9 @@ jobs:
       - name: install LLVM on Windows
         if: matrix.os == 'windows-latest'
         run: choco install llvm -y
-      - name: Environment
-        run: |
-          echo ::set-env name=RUST_BACKTRACE::full
       - name: Run tests
+        env:
+          RUST_BACKTRACE: full
         uses: actions-rs/cargo@v1
         with:
           command: test