Please tell me how to use proxy authentication?

I want to use localhost proxy to access my remote service, but failed, remote service return 407 Proxy Authorization Required
I use follow cmd:
`oha -n 100 --burst-delay 2s --burst-rate 10 -a "admin:123432" -x http://127.0.0.1:38520 "https://api.test.example.com`

oha --debug
`Request {
method: GET,
uri: /geoip,
version: HTTP/1.1,
headers: {
"accept": "*/*",
"accept-encoding": "gzip, compress, deflate, br",
"user-agent": "oha/1.8.0",
"host": "api.ip.sb",
"authorization": "Basic YWRtaW46MTIzNDMy",
},
body: Full {
data: None,
},
}
Error: no upgrade available`