code: func (e EventBuilder) ToEvent(channel, pattern string) Event {
  	fields := make([]Field, len(e.fields))
  	copy(fields, e.fields)
  
  	return Event{
  		fields:  fields,
  		kind:    e.kind,
  		channel: channel,
  		pattern: pattern,
  	}
  }
docs: // ToEvent converts an EventBuilder into an immutable event which appears
  // to have been send down the provided channel and pattern. This is primarily
  // used internally but may also be useful for unit testing.