why error https://test.ustc.edu.cn/

[aogg]

Using local JSON server list from stdin
Error when fetching server list: unexpected end of JSON input
Terminated due to error

git clone https://github.com/librespeed/speedtest-cli.git
cd speedtest-cli
 docker build -t librespeed-cli:latest .
 echo '[{"id": 1,"name": "a","server": "https://test.ustc.edu.cn/","dlURL": "garbage.php","ulURL": "empty.php","pingURL": "empty.php","getIpURL": "getIP.php"}]' | docker run --rm --name librespeed-cli librespeed-cli --local-json -