You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: client.go
    path of file: ./repos/qt/internal/examples/grpc/hello_world
    
    the code of the file until where you have to start completion: //hello.proto and this code is taken from: https://github.com/kenshaw/go-jakarta/tree/master/02-gomobile-and-grpc

package main

import (
	"errors"
	"time"

	"golang.org/x/net/conte
    
func (hc *HelloClient) SayHello(s string) (string, error) {
	// create request
	req := &HelloRequest{Greeting: s}

	// some safety checking
	if hc.conn == nil || hc.client == nil {
		return "", errors.New("unable to SayHello")
	}

	// call method
	res, err := hc.client.SayHello(context.Background(), req)
	if err != nil {
		return "", err
	}

	return res.Reply, nil
}