http range request, curl range header,

 http by default allows partial request, so browser/curl can resume download when using range header

to see if server allows partial transmission of data :

https://developer.mozilla.org/en-US/docs/Web/HTTP/Range_requests

BASH

curl -I http://i.imgur.com/z4d4kWk.jpg

HTTP

HTTP/1.1 200 OK
…
Accept-Ranges: bytes
Content-Length: 146515

If server response Accept-Ranges: byte, then server accepts partial

For GO gin, c.FileAttachement enable or r.static at router level enables range

https://pkg.go.dev/github.com/gin-gonic/gin#Context.File

func (c *Context) FileAttachment(filepath, filename string)

for curl you can request range 

https://everything.curl.dev/http/ranges.html

For browser set up for resumable download visit:
https://stackoverflow.com/questions/38200426/detecting-when-the-browser-has-requested-to-download-a-file

Each time you will get some content  and http response 206
The HTTP 206 Partial Content success status response code indicates that the request has succeeded and the body contains the requested ranges of data, as described in the Range header of the request.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/206
curl -r 0-199 http://example.com
Or everything in the file starting from index 200:
curl -r 200- http://example.com
Get 200 bytes from index 0 and 200 bytes from index 1000:
curl -r 0-199,1000-1199 http://example.com/