CI: Obtain rust-version dynamically

Read the 'rust-version' from Cargo.toml.

Signed-off-by: Erdem Meydanli <[email protected]>

.github/workflows/ci.yml

@@ -12,12 +12,24 @@ env:
     RUSTFLAGS: -Dwarnings
 
 jobs:
+    init:
+        name: Initialize the common variables
+        runs-on: ubuntu-latest
+        outputs:
+          msrv: ${{ step.rust.outputs.msrv }}
+          matrix: ${{ step.matrix.outputs.value }}
+        steps:
+          - id: rust
+            run: echo "::set-output name=msrv::${$(cat Cargo.toml | grep rust-version | tr -d '\"'):2:3}"
+          - id: matrix
+            run: echo "::set-output name=value::{\"rust\":["${{ step.rust.outputs.msrv }}", \"nightly\", \"stable\"]}"
+
     test:
         name: Test on rust ${{matrix.rust}}
         runs-on: ubuntu-latest
+        needs: init
         strategy:
-            matrix:
-                rust: [1.58.1, stable, nightly]
+            matrix: ${{fromJSON(needs.init.outputs.matrix)}}
         steps:
         - uses: actions/checkout@v2
         - uses: dtolnay/rust-toolchain@master