add Span

Author: vito

span.go

@@ -0,0 +1,17 @@
+package progrock
+
+import (
+	"context"
+
+	"github.com/opencontainers/go-digest"
+)
+
+// Span ties together lower-level Progrock APIs to provide a higher-level
+// OpenTelemetry-style API, using a Vertex like a span.
+func Span(ctx context.Context, id, name string, opts ...VertexOpt) (context.Context, *VertexRecorder) {
+	rec := FromContext(ctx)
+	vtx := rec.Vertex(digest.Digest(id), name, opts...)
+	rec = rec.WithParent(vtx.Vertex.Id)
+	ctx = ToContext(ctx, rec)
+	return ctx, vtx
+}