Request body is never shown in the failure dump (and Content-Length contradicts it)

[korya]

Problem

writeHttpDetails calls req.Write(w) after the transport has already drained the request body reader, so the dump shows headers with a non-zero Content-Length and no body.

Reproduction

$ http-assert -X POST -d 'THIS-IS-THE-REQUEST-BODY' --assert-status 999 http://127.0.0.1:8791/echo
…
FAILED: POST http://127.0.0.1:8791/echo (HTTP/1.1)

POST /echo HTTP/1.1
Host: 127.0.0.1:8791
User-Agent: Go-http-client/1.1
Content-Length: 24          ← claims 24 bytes
                            ← ships zero

Why it matters

When a POST assertion fails, the first question is "what did I actually send?" — and that is exactly what the dump omits. The output is also self-contradictory as an HTTP message.

Affected code

main.go — Client.writeHttpDetails, called from Client.Do

Suggested fix

Buffer the -d payload and set req.GetBody, then re-attach a fresh reader before dumping (or keep the raw string alongside the request and print it explicitly).