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: enable.go
    path of file: ./repos/streamdal/apps/server/vendor/github.com/aws/aws-sdk-go/aws/csm
    
    the code of the file until where you have to start completion: package csm

import (
	"fmt"
	"strings"
	"sync"
)

var (
	lock sync.Mutex
)

const (
	// DefaultPort is used when no port is specified.
	DefaultPort = "31000"

	// DefaultHost is the host that will be used when none is specified.
	DefaultHost = "127.0.0.1"
)

// AddressWithDefaults returns a CSM address built from the host and port
// values. If the host or port is not set, default values will be used
// instead. If host is "localhost" it will be replaced with "127.0.0.1".
    
func Start(clientID string, url string) (*Reporter, error) {
	lock.Lock()
	defer lock.Unlock()

	if sender == nil {
		sender = newReporter(clientID, url)
	} else {
		if sender.clientID != clientID {
			panic(fmt.Errorf("inconsistent client IDs. %q was expected, but received %q", sender.clientID, clientID))
		}

		if sender.url != url {
			panic(fmt.Errorf("inconsistent URLs. %q was expected, but received %q", sender.url, url))
		}
	}

	if err := connect(url); err != nil {
		sender = nil
		return nil, err
	}

	return sender, nil
}