POST with body does not work

[paramaw]

When doing POST with a request body, it drops the connection:

curl -X POST 'https://postman-echo.com/post' -H 'X-DH-Cache-Freshness: now' -H "Content-Type: application/json" --data '{"hello":"world"}' -kv --proxy http://localhost:2933                      
Note: Unnecessary use of -X or --request, POST is already inferred.
...
> POST /post HTTP/1.1
> Host: postman-echo.com
> User-Agent: curl/7.58.0
> Accept: */*
> X-DH-Cache-Freshness: now
> Content-Type: application/json
> Content-Length: 17
>
* upload completely sent off: 17 out of 17 bytes
* Connection #0 to host localhost left intact