[BUG] C++ sdk example get grpc error

[yhmo]

Describe the bug
Start Milvus server, then run C++ sdk example(sdk_simple) from command line. The example program get grpc error.

Steps/Code to reproduce behavior
1 .Start Milvus server
2. Run C++ sdk example(sdk_simple) from command line

Expected behavior
The example should run successfully.

Environment details

• Milvus version (v0.5.0)
• Default setting

[yhmo]

When your sdk encounter "grpc failed" or "socket closed" error, the reason may be that your terminal has set http_proxy, use a terminal without http_proxy can solve the error.