Support the environment variable propagation

[adrielp]

With the environment variable context propagation spec being added, we'd like to have its support added to Go. This is part of a larger effort to adding support in each of the currently supported languages.

Two example pull requests have been opened in the past that can be used for ideas in conjunction with the specification.

• [Prototype] propagation: add EnvCarrier opentelemetry-go#6778
• Add EnvironmentCarrier for propagating trace information across processes opentelemetry-go#2931

[pellared]

I suggest moving this issue to Go Contrib and implement it under https://github.com/open-telemetry/opentelemetry-go-contrib/tree/main/propagators since it is not a required propagator.

[adrielp]

Ok, thanks for that information @pellared - I see it's already been moved. Since it's been added to the v1.40.0 milestone @MrAlias, is someone already geared to take this on from the contrib side?

[Joibel]

@pellared - I'd like to check that what we want to happen here is a Carrier similar to open-telemetry/opentelemetry-go#6778, even though the suggestion is to go into /propagators, which currently only contains propogators.

There is a subtle difference in directory naming, in opentelemetry-go the directory is called propogation instead of propogators.