type Span struct {
    Name     string
    ID       SpanContext
    ParentID SpanID
    Start    time.Time
    Finish   time.Time
    Tags     TagList
    Events   []Event
}

type SpanData struct {
    SpanContext
    ParentSpanID SpanID
    SpanKind     int
    Name         string
    StartTime    time.Time
    // The wall clock time of EndTime will be adjusted to always be offset
    // from StartTime by the duration of the span.
    EndTime time.Time
    // The values of Attributes each have type string, bool, or int64.
    Attributes    map[string]interface{}
    Annotations   []Annotation
    MessageEvents []MessageEvent
    Status
    Links                    []Link
    HasRemoteParent          bool
    DroppedAttributeCount    int
    DroppedAnnotationCount   int
    DroppedMessageEventCount int
    DroppedLinkCount         int

    // ChildSpanCount holds the number of child span created for this span.
    ChildSpanCount int
}