func OperationName(operationName string) ClientOption {
	return func(options *clientOptions) {
		options.operationName = operationName
	}
}
OperationName returns a ClientOption that sets the operation
name for the client-side span.
package nethttp
import (
	"context"
	"io"
	"net/http"
	"net/http/httptrace"
	"net/url"
	"github.com/opentracing/opentracing-go"
	"github.com/opentracing/opentracing-go/ext"
	"github.com/opentracing/opentracing-go/log"
)
type contextKey int
const (
	keyTracer contextKey = iota
)
const defaultComponentName = "net/http"
type Transport struct {
	http.RoundTripper
}
type clientOptions struct {
	operationName            string
	componentName            string
	urlTagFunc               func(u *url.URL) string
	disableClientTrace       bool
	disableInjectSpanContext bool
	spanObserver             func(span opentracing.Span, r *http.Request)
}
type ClientOption func(*clientOptions)