Imports of client command

PathSynopsis
contextPackage context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.
flagPackage flag implements command-line flag parsing.
google.golang.org/grpcPackage grpc implements an RPC system called gRPC.
google.golang.org/grpc/examples/features/proto/echo
logPackage log implements a simple logging package.
timePackage time provides functionality for measuring and displaying time.