grpc/ttnctx/context.go
func KeyFromIncomingContext(ctx context.Context) (string, error) {
	md := MetadataFromIncomingContext(ctx)
	return KeyFromMetadata(md)
}
func KeyFromIncomingContext(ctx context.Context) (string, error) {
	md := MetadataFromIncomingContext(ctx)
	return KeyFromMetadata(md)
}
// KeyFromIncomingContext gets the key from the incoming context or returns ErrNoKey