# Functions
MDFromIncomingContext extracts incoming MD from context or nil if not found.
MDFromOutgoingContext extracts outgoing MD from context or nil if not found.
NewIncomingContextWithMD creates a new context with incoming MD attached.
NewMetaDataFromMD creates a MetaData from MD.
NewMetaDataPairs creates a MetaData from key/value pairs.
NewOutgoingContextWithMD creates a new context with outgoing MD attached.
# Variables
EmptyMD is an empty MD.
# Interfaces
MD is used to carry extra key/value context data (meta data) from outgoing side to incoming side.
# Type aliases
MetaData is the default implementation of MD.