feat: login get to post (#13)

shenyu-client-core/src/main/java/org/apache/shenyu/client/core/utils/RegisterUtils.java

diff --git a/shenyu-client-core/src/main/java/org/apache/shenyu/client/core/utils/RegisterUtils.java b/shenyu-client-core/src/main/java/org/apache/shenyu/client/core/utils/RegisterUtils.java
index 544c511..93219ac 100644
--- a/shenyu-client-core/src/main/java/org/apache/shenyu/client/core/utils/RegisterUtils.java
+++ b/shenyu-client-core/src/main/java/org/apache/shenyu/client/core/utils/RegisterUtils.java
@@ -139,7 +139,7 @@
         Map<String, Object> loginMap = new HashMap<>(2);
         loginMap.put(Constants.LOGIN_NAME, username);
         loginMap.put(Constants.PASS_WORD, password);
-        String result = OkHttpTools.getInstance().get(url, loginMap);
+        String result = OkHttpTools.getInstance().post(url, GsonUtils.getInstance().toJson(loginMap));
         Map<String, Object> resultMap = GsonUtils.getInstance().convertToMap(result);
         if (!String.valueOf(CommonErrorCode.SUCCESSFUL).equals(String.valueOf(resultMap.get(Constants.ADMIN_RESULT_CODE)))) {
             return Optional.empty();