Update CI to use go 1.18

Author: alvaroaleman

.github/workflows/test.yml

@@ -4,7 +4,7 @@ jobs:
   build:
     strategy:
       matrix:
-        go-versions: [1.13.x]
+        go-versions: [1.18.0]
         platform: [windows-latest]
     runs-on: ${{ matrix.platform }}
     steps:
@@ -24,7 +24,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-versions: [1.12.x, 1.13.x, 1.14.x]
+        go-versions: [1.18.0]
         platform: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.platform }}
     steps:
@@ -56,7 +56,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v1
         with:
-          go-version: 1.13.x
+          go-version: 1.18.0
       - name: Add GOBIN to PATH
         run: echo "$(go env GOPATH)/bin" >> $GITHUB_PATH
       - name: Install dependencies