Use go1.18 in CI as well

Author: parkr

.github/workflows/ci.yaml

@@ -1,5 +1,5 @@
 ---
-on: 
+on:
 - push
 - pull_request
 name: Test
@@ -10,7 +10,7 @@ jobs:
     - name: Install Go
       uses: actions/setup-go@v2
       with:
-        go-version: 1.16.x
+        go-version: 1.18.x
     - name: Checkout code
       uses: actions/checkout@v2
     - name: Test