fix code style

1. add .clang-format code style file.
2. format code of core.

use `clang-format -i -style=file ./core/*/*.cc ./core/*/*.h` command to format

core/src/StsAssumeRoleCredentialsProvider.cc

@@ -1,18 +1,18 @@
 /*
-* Copyright 1999-2019 Alibaba Cloud All rights reserved.
-*
-* Licensed under the Apache License, Version 2.0 (the "License");
-* you may not use this file except in compliance with the License.
-* You may obtain a copy of the License at
-*
-*      http://www.apache.org/licenses/LICENSE-2.0
-*
-* Unless required by applicable law or agreed to in writing, software
-* distributed under the License is distributed on an "AS IS" BASIS,
-* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-* See the License for the specific language governing permissions and
-* limitations under the License.
-*/
+ * Copyright 1999-2019 Alibaba Cloud All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 
 #include <alibabacloud/core/StsAssumeRoleCredentialsProvider.h>
 #include <iomanip>
@@ -21,25 +21,15 @@
 namespace AlibabaCloud {
 
 StsAssumeRoleCredentialsProvider::StsAssumeRoleCredentialsProvider(
-    const Credentials &credentials,
-    const ClientConfiguration &configuration,
-    const std::string & roleArn,
-    const std::string & roleSessionName,
-    const std::string & policy,
-    int durationSeconds):
-  CredentialsProvider(),
-  StsClient(credentials, configuration),
-  roleArn_(roleArn),
-  roleSessionName_(roleSessionName),
-  policy_(policy),
-  durationSeconds_(durationSeconds),
-  cachedMutex_(),
-  cachedCredentials_("", ""),
-  expiry_() {
-}
+    const Credentials &credentials, const ClientConfiguration &configuration,
+    const std::string &roleArn, const std::string &roleSessionName,
+    const std::string &policy, int durationSeconds)
+    : CredentialsProvider(), StsClient(credentials, configuration),
+      roleArn_(roleArn), roleSessionName_(roleSessionName), policy_(policy),
+      durationSeconds_(durationSeconds), cachedMutex_(),
+      cachedCredentials_("", ""), expiry_() {}
 
-StsAssumeRoleCredentialsProvider::~StsAssumeRoleCredentialsProvider() {
-}
+StsAssumeRoleCredentialsProvider::~StsAssumeRoleCredentialsProvider() {}
 
 Credentials StsAssumeRoleCredentialsProvider::getCredentials() {
   loadCredentials();
@@ -47,10 +37,10 @@ Credentials StsAssumeRoleCredentialsProvider::getCredentials() {
   return cachedCredentials_;
 }
 
-bool StsAssumeRoleCredentialsProvider::checkExpiry()const {
+bool StsAssumeRoleCredentialsProvider::checkExpiry() const {
   auto now = std::chrono::system_clock::now();
   auto diff =
-  std::chrono::duration_cast<std::chrono::seconds>(now - expiry_).count();
+      std::chrono::duration_cast<std::chrono::seconds>(now - expiry_).count();
 
   return (diff > 0 - 60);
 }
@@ -69,8 +59,8 @@ void StsAssumeRoleCredentialsProvider::loadCredentials() {
       if (assumeRoleOutcome.isSuccess()) {
         const auto stsCredentials = assumeRoleOutcome.result().credentials();
         cachedCredentials_ = Credentials(stsCredentials.accessKeyId,
-          stsCredentials.accessKeySecret,
-          stsCredentials.securityToken);
+                                         stsCredentials.accessKeySecret,
+                                         stsCredentials.securityToken);
 
         std::tm tm = {};
 #if defined(__GNUG__) && __GNUC__ < 5
@@ -85,4 +75,4 @@ void StsAssumeRoleCredentialsProvider::loadCredentials() {
   }
 }
 
-}  // namespace AlibabaCloud
+} // namespace AlibabaCloud