improve direct string warning

cmd/mongo_struct.go

@@ -43,6 +43,9 @@ const (
 	mLogKeyHostId = mLogKeyHostInfo + "." + mLogKeyId
 )
 
+// Don't use direct strings in bson types. Use the constants as keys.
+// This ensures keys (and subkeys) are consistent, at least within the package.
+
 const (
 	mLogKeyHostInfo = "host_info"
 	mLogKeyId       = "id"
@@ -59,7 +62,6 @@ const (
 
 // not using marshal, since it is <0.1x performance
 func (l *mLog) toBson() bson.M {
-	// DO NOT USE QUOTED STRINGS! Move them to const and use variable instead
 	return bson.M{
 		mLogKeyHostInfo: bson.M{
 			mLogKeyId:   l.HostInfo.Id,