chore: add checkfmt.sh in workflows

.github/workflows/go.yml

@@ -14,18 +14,21 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v4
         with:
           go-version: 1.21
 
+      - name: Fmt
+        run: ./checkfmt.sh
+
+      - name: Vet
+        run: go vet ./...
+
       - name: Build
         run: go build ./...
 
       - name: Test
         run: go test -race ./...
-
-      - name: Vet
-        run: go vet ./...

checkfmt.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+go install golang.org/x/tools/cmd/goimports
+
+HAS_FMT_ERR=0
+# For every Go file in the project, excluding vendor...
+
+for file in $(go list -f '{{$dir := .Dir}}{{range .GoFiles}}{{printf "%s/%s\n" $dir .}}{{end}}{{range .TestGoFiles}}{{printf "%s/%s\n" $dir .}}{{end}}{{range .IgnoredGoFiles}}{{printf "%s/%s\n" $dir .}}{{end}}{{range .CgoFiles}}{{printf "%s/%s\n" $dir .}}{{end}}' ./... ); do
+  # ... if file does not contain standard generated code comment (https://golang.org/s/generatedcode)...
+  if ! grep -Exq '^// Code generated .* DO NOT EDIT\.$' $file; then
+    FMT_OUT="$(goimports -l -d $file)"
+    # ... and if goimports had any output...
+    if [[ -n "$FMT_OUT" ]]; then
+      if [ "$HAS_FMT_ERR" -eq "0" ]; then
+        # Only print this once.
+        HAS_FMT_ERR=1
+        echo 'Commit includes files that are not gofmt-ed' && \
+        echo 'run "make fmt"' && \
+        echo ''
+      fi
+      echo "$FMT_OUT" # Print output and continue, so developers don't fix one file at a t
+    fi
+   fi
+done
+
+## print at the end too... sometimes it is nice to see what to do at the end.
+if [ "$HAS_FMT_ERR" -eq "1" ]; then
+    echo 'Commit includes files that are not gofmt-ed' && \
+    echo ''
+fi
+exit "$HAS_FMT_ERR"