add gofmt verify in CI

Signed-off-by: Crazykev <crazykev@zju.edu.cn>

hack/verify-gofmt.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+find_files() {
+  find . -not \( \
+      \( \
+        -wholename '*/vendor/*' \
+      \) -prune \
+    \) -name '*.go'
+}
+
+GOFMT="gofmt -s"
+bad_files=$(find_files | xargs $GOFMT -l)
+if [[ -n "${bad_files}" ]]; then
+  echo "!!! '$GOFMT' needs to be run on the following files: "
+  echo "${bad_files}"
+  exit 1
+fi