feat: add code comment

Signed-off-by: Xinwei Xiong(cubxxw-openim) <3293172751nss@gmail.com>

scripts/coverage.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+
+# http://stackoverflow.com/a/21142256/2055281
+
+echo "mode: atomic" > coverage.txt
+
+for d in $(find ./* -maxdepth 10 -type d); do
+    if ls $d/*.go &> /dev/null; then
+        go test  -coverprofile=profile.out -covermode=atomic $d
+        if [ -f profile.out ]; then
+            cat profile.out | grep -v "mode: " >> /tmp/coverage.txt
+            rm profile.out
+        fi
+    fi
+done
+