code: func WithVersion(ctx context.Context, version string) context.Context {
  	ctx = context.WithValue(ctx, versionKey{}, version)
  	// push a new logger onto the stack
  	return WithLogger(ctx, GetLogger(ctx, versionKey{}))
  }
docs: // WithVersion stores the application version in the context. The new context
  // gets a logger to ensure log messages are marked with the application
  // version.