The propagation package is a highly generic package and it requires users to implement common cases from scratch by implementing the interfaces. Two of these interfaces are implementation with the builtin map type and a carrier that works with a request object.

It's be useful to provide two Carrier implementations out of the box from the SDK or somewhere else:

func NewMapCarrier(m map[string][]byte) propagation.Carrier
func NewHeaderCarrier(h http.Header) propagation.Carrier