Failure downloading stage 0 Go: no progress for 20 seconds, then checksum failure

It looks like the download doesn't make progress for a while (20 seconds), then fails when checking the checksum. I assume the file's truncated. I'm not sure why curl itself isn't reporting an error:

https://dev.azure.com/dnceng/internal/_build/results?buildId=1186727&view=logs&j=d64f3f73-a65e-5047-8380-514dab748946&t=8bc915d5-88fc-5303-cb01-49be6dc3eb68&l=42

Downloading stage 0 Go compiler and extracting to '/home/vsts_azpcontainer/.go-stage-0/1.16' ...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
100    73  100    73    0     0   1216      0 --:--:-- --:--:-- --:--:--  1216

  0     0    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:02 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:03 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:04 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:05 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:06 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:07 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:08 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:09 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:10 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:11 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:12 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:13 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:14 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:15 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:16 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:17 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:18 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:19 --:--:--     0
  0     0    0     0    0     0      0      0 --:--:--  0:00:20 --:--:--     0
100  1613  100  1613    0     0     78      0  0:00:20  0:00:20 --:--:--   369
/home/vsts_azpcontainer/.go-stage-0/1.16/go.tar.gz: FAILED
sha256sum: WARNING: 1 computed checksum did NOT match

For comparison, a healthy download from another job in that build (completed in 5 seconds):

https://dev.azure.com/dnceng/internal/_build/results?buildId=1186727&view=logs&j=0062eaab-e429-5c7e-1d0d-476982c7b962&t=f4a61628-2565-5334-9bea-d42b30749d7a&l=24

Downloading stage 0 Go compiler and extracting to '/home/vsts_azpcontainer/.go-stage-0/1.16' ...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
100    73  100    73    0     0    646      0 --:--:-- --:--:-- --:--:--   646

 96  123M   96  118M    0     0   119M      0  0:00:01 --:--:--  0:00:01  119M
100  123M  100  123M    0     0   120M      0  0:00:01  0:00:01 --:--:--  129M
/home/vsts_azpcontainer/.go-stage-0/1.16/go.tar.gz: OK
Done extracting stage 0 Go compiler to '/home/vsts_azpcontainer/.go-stage-0/1.16'

If it's simply flaky, this will be fixed by using a Docker container: #5.

Start with the stage 0 Go compiler download step that writes to /home/vsts_azpcontainer/.go-stage-0/1.16/go.tar.gz, and compare the failing and healthy Azure build logs linked in the issue. Investigate why curl can pause and produce a truncated archive without reporting an error. Done means the download either completes with a valid checksum or reports a clear failure for this condition.