THRIFT-5969: Enforce gofmt -s in CI

Author: fishy

.github/workflows/build.yml

@@ -247,6 +247,13 @@ jobs:
         with:
           go-version: ${{ matrix.go }}
 
+      - name: Check gofmt
+        # Args:
+        # -s: Simplify code
+        # -d: Display changes, and exit non-zero when changes present
+        # -e: Report all errors instead of only the first 10
+        run: gofmt -s -d -e $(git ls-files | grep "\.go$")
+
       - name: Install dependencies
         run: |
           sudo apt-get update -yq