Bump matrix of supported Go versions

to test on the latest release (^1.18) and drop testing/supporting ^1.15.

.github/workflows/cli.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        go: [1.15, 1.16, 1.17]
+        go: [^1.16, ^1.17, ^1.18]
     name: ${{ matrix.os }} @ Go ${{ matrix.go }}
     runs-on: ${{ matrix.os }}
     steps:
@@ -38,7 +38,7 @@ jobs:
           ref: ${{ github.ref }}
 
       - name: GOFMT Check
-        if: matrix.go == 1.17 && matrix.os == 'ubuntu-latest'
+        if: matrix.go == '^1.17' && matrix.os == 'ubuntu-latest'
         run: test -z $(gofmt -l .)
 
       - name: vet
@@ -51,7 +51,7 @@ jobs:
         run: go run internal/build/build.go check-binary-size
 
       - name: Upload coverage to Codecov
-        if: success() && matrix.go == 1.17 && matrix.os == 'ubuntu-latest'
+        if: success() && matrix.go == '^1.17' && matrix.os == 'ubuntu-latest'
         uses: codecov/codecov-action@v1
         with:
           fail_ci_if_error: true
@@ -63,8 +63,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v1
         with:
-          # Currently fails on 1.16+
-          go-version: 1.15
+          go-version: ^1.18
 
       - name: Use Node.js 12.x
         uses: actions/setup-node@v1