ci: speed up github actions

.github/workflows/ci.yml

@@ -29,6 +29,24 @@ jobs:
         toolchain: ${{ matrix.rust }}
         override: true
 
+    - name: Cache cargo registry
+      uses: actions/cache@v1
+      with:
+        path: ~/.cargo/registry
+        key: ${{ matrix.os }}-${{ matrix.rust }}-cargo-registry-${{ hashFiles('**/Cargo.toml') }}
+
+    - name: Cache cargo index
+      uses: actions/cache@v1
+      with:
+        path: ~/.cargo/git
+        key: ${{ matrix.os }}-${{ matrix.rust }}-cargo-index-${{ hashFiles('**/Cargo.toml') }}
+
+    - name: Cache cargo build
+      uses: actions/cache@v1
+      with:
+        path: target
+        key: ${{ matrix.os }}-${{ matrix.rust }}-cargo-build-target-${{ hashFiles('**/Cargo.toml') }}
+
     - name: check
       uses: actions-rs/cargo@v1
       with:
@@ -66,12 +84,6 @@ jobs:
         command: test
         args: --all --features "unstable attributes"
 
-    - name: documentation test
-      uses: actions-rs/cargo@v1
-      with:
-        command: test
-        args: --doc --features "unstable attributes"
-
   build__with_no_std:
     name: Build with no-std
     runs-on: ubuntu-latest
@@ -117,15 +129,3 @@ jobs:
 
     - name: Docs
       run: cargo doc --features docs
-
-  # clippy_check:
-  #   name: Clippy check
-  #   runs-on: ubuntu-latest
-  #   steps:
-  #     - uses: actions/checkout@v1
-  #     - name: Install rust
-  #       run: rustup update beta && rustup default beta
-  #     - name: Install clippy
-  #       run: rustup component add clippy
-  #     - name: clippy
-  #       run: cargo clippy --all --features unstable