go-client.11.go

bob := client.FlatFeed("user", "bob")
alice := client.NotificationFeed("notification", "alice")
activity := stream.Activity{
  Actor:     "user:bob",
  Verb:      "tweet",
  Object:    "hanging out with @alice and @carol",
  ForeignID: "fid:123",
  Time:      stream.Time{time.Now()},
  To: []string{
    alice.ID(),
    "notification:carol",
  },
}
// alice's and carol's notification feeds will receive the activity.
_, err := bob.AddActivity(activity)
if err != nil {
  // ...
}

// Update the "to" targets of the activity so that it's sent to david but not to
// carol anymore
err = bob.UpdateToTargets(activity,
  stream.WithToTargetsAdd("notification:david"),
  stream.WithToTargetsRemove("notification:carol"),
)
if err != nil {
  // ...
}