Usage of /usr/bin/codegen:
      --impl string        type implementing the interface (default "gRPCVtctldClient")
      --local              generate a local, in-process client rather than a grpcclient
      --out string         output destination. leave empty to use stdout
      --source string      source package (default "../../proto/vtctlservice")
      --targetpkg string   package name to generate code for (default "grpcvtctldclient")
      --type string        interface type to implement (default "VtctldClient")