Make use of NLL to clean up handshaking logic (#576)

.github/workflows/CI.yml

@@ -83,3 +83,32 @@ jobs:
       - name: Check minimal versions
         run: cargo clean; cargo update -Zminimal-versions; cargo check
         if: matrix.rust == 'nightly'
+
+  msrv:
+    name: Check MSRV (${{ matrix.rust }})
+    needs: [style]
+    strategy:
+      matrix:
+        rust:
+          - 1.46 # never go past Hyper's own MSRV
+
+        os:
+          - ubuntu-latest
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v1
+
+      - name: Install Rust (${{ matrix.rust }})
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: ${{ matrix.rust }}
+          override: true
+
+      - name: Check
+        uses: actions-rs/cargo@v1
+        with:
+          command: check