Spec Conformance Review: Span Get Context

[MrAlias]

• Review Get Context operation for a Span and identify all normative requirements it contains.
• Validate our implementation of the specification to conform or not. If it conforms, document the conformity here. If it does not open an Issue or PR track the work.

[MrAlias]

Span -- Get Context

The Span interface MUST provide:
An API that returns the SpanContext for the given Span.

SpanContext method

The returned value may be used even after the Span is finished.

✔️, the returned SpanContext is immutable by definition from the specification and we (intend to) implement it as such.

The returned value MUST be the same for the entire Span lifetime.

The only time a SpanContext is set is during initialization.

This MAY be called GetContext.

We call it SpanContext to conform with our design guidelines: https://golang.org/doc/effective_go#Getters