span

const (
	// SpanKindUnspecified is an unspecified SpanKind and is not a valid
	// SpanKind. SpanKindUnspecified should be replaced with SpanKindInternal
	// if it is received.
	SpanKindUnspecified SpanKind = 0
	// SpanKindInternal is a SpanKind for a Span that represents an internal
	// operation within an application.
	SpanKindInternal SpanKind = 1
	// SpanKindServer is a SpanKind for a Span that represents the operation
	// of handling a request from a client.
	SpanKindServer SpanKind = 2
	// SpanKindClient is a SpanKind for a Span that represents the operation
	// of client making a request to a server.
	SpanKindClient SpanKind = 3
	// SpanKindProducer is a SpanKind for a Span that represents the operation
	// of a producer sending a message to a message broker. Unlike
	// SpanKindClient and SpanKindServer, there is often no direct
	// relationship between this kind of Span and a SpanKindConsumer kind. A
	// SpanKindProducer Span will end once the message is accepted by the
	// message broker which might not overlap with the processing of that
	// message.
	SpanKindProducer SpanKind = 4
	// SpanKindConsumer is a SpanKind for a Span that represents the operation
	// of a consumer receiving a message from a message broker. Like
	// SpanKindProducer Spans, there is often no direct relationship between
	// this Span and the Span that produced the message.
	SpanKindConsumer SpanKind = 5
)