go.mod update causes dependency issues

Nobody has claimed this yet.

Not exactly sure what dependency change made this happen, but if I use goth `v1.65.0`, a bunch of unrelated dependencies get forced to a newer version in my app. Snapshot of `go.mod` in the app

```
- github.com/golang/mock v1.4.3
- github.com/golang/protobuf v1.4.1
- github.com/google/go-cmp v0.4.1
+ github.com/golang/mock v1.4.4
+ github.com/golang/protobuf v1.4.2
+ github.com/google/go-cmp v0.5.2
......omitted......
- golang.org/x/net v0.0.0-20200904194848-62affa334b73
- golang.org/x/sys v0.0.0-20200509044756-6aff5f38e54f // indirect
- golang.org/x/tools v0.0.0-20200331025713-a30bf2db82d4
- google.golang.org/api v0.29.0 // indirect
- google.golang.org/genproto v0.0.0-20200513103714-09dca8ec2884
- google.golang.org/grpc v1.30.0
+ golang.org/x/net v0.0.0-20200930145003-4acb6c075d10
+ golang.org/x/tools v0.0.0-20200929161345-d7fc70abf50f
+ google.golang.org/genproto v0.0.0-20200929141702-51c3e5b607fe
+ google.golang.org/grpc v1.32.0
```

Normally this would be OK, but it seems that protobuf has actually gone up a major version from v1.4.1 to v1.4.2, so code that uses protos now get the error

```
undefined: "github.com/golang/protobuf/proto".ProtoPackageIsVersion4
```

I confirmed that `v1.64.2` is fine, so I suspect the change was due to https://github.com/markbates/goth/pull/364. Would you consider undoing the `go.mod` updates there?

Start by comparing the go.mod changes introduced in PR #364 and reproducing the dependency graph with goth v1.65.0 versus v1.64.2. Confirm whether the ProtoPackageIsVersion4 failure is caused by those updates; done means the dependency resolution no longer forces incompatible protobuf versions and the reported application case builds.

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