A little update after getting the idea that I can easily debug with nc: curl
"correct" request:
--------------------------c6d4d41bf1581405
Content-Disposition: form-data; name="file"; filename="1.txt"
Content-Type: text/plain
Abspath: /home/sgm/1.txt
123
--------------------------c6d4d41bf1581405--
Run
nim result, with the code below:
--4292486321577947087
Content-Disposition: form-data; name="file"; filename="1.txt"
Content-Type: text/plain
123
--4292486321577947087
Content-Disposition: form-data; name="headers"
Abspath: /home/sgm/1.txt
--4292486321577947087--
Run