How to combine results of different HandleRPC events?

[LSTPro]

// HandleRPC implements per-RPC tracing and stats instrumentation.
func (c *statsHandler) HandleRPC(ctx context.Context, rs stats.RPCStats) {
switch rs := rs.(type) {

case *stats.InHeader:

 if rs.Client {
    fmt.Printf(rs.Header)
}

case *stats.End:
  ign := false
  c.lock.RLock()
  ign = c.ignore
  c.lock.RUnlock()

if !ign {
    duration := rs.EndTime.Sub(rs.BeginTime)

    var st string
    s, ok := status.FromError(rs.Error)
    if ok {
        st = s.Code().String()
    }

    c.results <- &callResult{rs.Error, st, duration, rs.EndTime}

    if c.hasLog {
        c.log.Debugw("Received RPC Stats",
            "statsID", c.id, "code", st, "error", rs.Error,
            "duration", duration, "stats", rs)
    }
}
}

}

I have the response metadata coming on event *stats.InHeader and the rest of grpc stats on event *stats.End, I want to combine metadata and grpc stats into one struct object callResult at the end of the grpc call. I am quite not sure how to realize this.