This makes it easier to reason about what this script is doing.

Mostly for texttospeech, per internal bug 122452555.

While we're in the $GOPATH transitionary period, a dependency could
accidentally find its way into our require statements without being codified in
go.mod/go.sum. This CL makes our CI check for such a case, and exit 1 if it
detects it.

Mostly for the new firestore/v1 protos

This reverts commit 73d5040b.

This does a regeneration using the version of protobuf specified in the
go.mod: v1.2.0.

This reverts commit 3360461a.

This commit was generated by go mod init && go mod tidy

This regeneration pulls in the latest generator
change that deprecates x/net/context in favour
of context. Since we no longer support Go
versions below 1.9, context is preferred.

regen

* regenerate

* using latest protoc-gen-go

should be fixed in https://github.com/grpc/grpc-go/pull/2242#pullrequestreview-140912658 (#86)