Update README.md (#155)

Co-authored-by: wangbin13 <wangbin13@corp.netease.com>

README.md

@@ -413,7 +413,7 @@ what was the previous value that this operation was overwritten. You can do that
     else
       std::cout << "operation failed, details: " << response.error_message();
   }
-  catch (std::ecxeption const & ex)
+  catch (std::exception const & ex)
   {
     std::cerr << "communication problem, details: " << ex.what();
   }