bug#49202: guix import go type error (failed regex match?)

[raingloom <raingloom@riseup.net>]

When I run
guix import go -r github.com/golang-migrate/migrate/v4
it works for a looong time (something else to work on I guess. maybe
fetching every git repo is not the best solution.) and then gives this
error:

In procedure vector-ref: Wrong type argument in position 1 (expecting
vector): #f


Trace:

```
following redirection to `https://go.mongodb.org/mongo-driver/'...
following redirection to `https://github.com/moby/moby?go-get=1'...
Backtrace:
In srfi/srfi-1.scm:
   586:29 19 (map1 _)
   586:29 18 (map1 _)
   586:29 17 (map1 _)
   586:29 16 (map1 _)
   586:29 15 (map1 _)
   586:29 14 (map1 (("github.com/cznic/mathutil" #f) ("github.…" …) …))
   586:17 13 (map1 (("github.com/containerd/containerd" #f) ("…" …) …))
In guix/import/utils.scm:
   466:33 12 (lookup-node "github.com/containerd/containerd" #f)
In guix/import/go.scm:
    646:5 11 (_ _ #:version _ #:repo _)
In ice-9/boot-9.scm:
  1752:10 10 (with-exception-handler _ _ #:unwind? _ # _)
In guix/import/go.scm:
   656:11  9 (_)
In guix/memoization.scm:
     98:0  8 (mproc "github.com/containerd/containerd" #:goproxy "h…" …)
In unknown file:
           7 (_ #<procedure 7fc8fd914c60 at guix/memoization.scm:17…> …)
In guix/import/go.scm:
   589:32  6 (go-module->guix-package "github.com/containerd/contai…" …)
In ice-9/ports.scm:
    472:4  5 (with-input-from-string _ _)
In guix/import/go.scm:
   359:10  4 (_)
In unknown file:
           3 (_ #<procedure 7fc90098cf30 at guix/import/go.scm:326:…> …)
In guix/import/go.scm:
   334:24  2 (replace-directive (("k8s.io/utils" "v0.0.0-20201…") …) …)
In ice-9/regex.scm:
   118:20  1 (match:substring #f _)
In ice-9/boot-9.scm:
  1685:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1685:16: In procedure raise-exception:
In procedure vector-ref: Wrong type argument in position 1 (expecting
vector): #f
```