gofmt GitHub action seems broken

[kele]

On this PR: https://github.com/google/go-safeweb/runs/4009332391?check_suite_focus=true

I get:

Run [ "$(gofmt -l $(find . -name '*.go') 2>&1)" = "" ]
  [ "$(gofmt -l $(find . -name '*.go') 2>&1)" = "" ]
  shell: /bin/bash -e {0}
  env:
    GOROOT: /opt/hostedtoolcache/go/1.17.2/x64
Error: Process completed with exit code 

There is little debugging information here, too. I think this should be changed.

[kele]

I think it fails because of https://golang.org/doc/go1.17#gofmt, judging by https://goreportcard.com/report/github.com/google/go-safeweb#gofmt.

[kele]

Fixed by #356