Using the base URL in path.Join caused it to remove the two slashes (because /////tmp == /tmp):
`https:/tildegit.org/api/v1/repos/owner/name`
Then, using that in URL.Parse causes it to see a `https:` scheme, and the / right afterwards means "start a path here", not a hostname, because hostnames begin with two slashes. That's a valid URL, with no hostname. Then it gets turned back into a string:
`https:///tildegit.org/api/v1/repos/owner/name`
That's another way of expressing the same URL with no hostname: //<empty hostname>/<path>.
curl, Firefox and Chromium all fix the triple slash automatically, but fasthttp doesn't, and it tries to look up the empty string as a DNS host!