Use nightly channel as CI default build toolchain

Author: tan-wei

.github/workflows/ci.yaml

@@ -11,7 +11,7 @@ jobs:
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: nightly
           override: true
       - uses: actions-rs/cargo@v1
         with:
@@ -25,7 +25,7 @@ jobs:
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: nightly
           override: true
       - uses: actions-rs/cargo@v1
         with:
@@ -39,7 +39,7 @@ jobs:
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: nightly
           override: true
       - run: rustup component add rustfmt
       - uses: actions-rs/cargo@v1
@@ -56,7 +56,7 @@ jobs:
   #     - uses: actions-rs/toolchain@v1
   #       with:
   #         profile: minimal
-  #         toolchain: stable
+  #         toolchain: nightly
   #         override: true
   #     - run: rustup component add clippy
   #     - uses: actions-rs/cargo@v1