fix: avoid coverage.out parsing issue on Windows

Split test step into two conditional steps:
- Run tests without coverage on Windows and macOS
- Run tests with coverage only on ubuntu-latest

This avoids PowerShell parsing '-coverprofile=coverage.out' as '.out' on Windows.

Author: ysyneu

.github/workflows/go.yml

@@ -27,6 +27,11 @@ jobs:
         run: go mod download
 
       - name: Run unit tests
+        if: matrix.os != 'ubuntu-latest'
+        run: go test -race ./...
+
+      - name: Run unit tests with coverage
+        if: matrix.os == 'ubuntu-latest'
         run: go test -race -coverprofile=coverage.out ./...
 
       - name: Build