type serverShutdownSignalKeyType … const serverShutdownSignalKey … type ServerShutdownSignal … // ServerShutdownSignalFrom returns the ServerShutdownSignal instance // associated with the request context. // If there is no ServerShutdownSignal asscoaied with the context, // nil is returned. func ServerShutdownSignalFrom(ctx context.Context) ServerShutdownSignal { … } // WithServerShutdownSignal returns a new context that stores // the ServerShutdownSignal interface instance. func WithServerShutdownSignal(parent context.Context, window ServerShutdownSignal) context.Context { … }