asFlow

val eventChannel: EventChannel<BotEvent> = ...
val flow: Flow<BotEvent> = eventChannel.asFlow()

flow.collect { // it
  //
}

flow.filterIsInstance<GroupMessageEvent>.collect { // it: GroupMessageEvent
  // 处理事件 ...
}

flow.filterIsInstance<FriendMessageEvent>.collect { // it: FriendMessageEvent
  // 处理事件 ...
}