Simplify GC life by zeroing references to closed worker chans and client conns

client.go

@@ -901,6 +901,7 @@ func (c *HostClient) connsCleaner() {
 			// Do not copy(c.conns, c.conns[1:]), since this may be
 			// quite slow for multi-million conns count.
 			// Just move c.conns one position ahead.
+			c.conns[0] = nil
 			c.conns = c.conns[1:]
 		}
 		if c.connsCount == 0 {

workerpool.go

@@ -87,6 +87,7 @@ func (wp *workerPool) clean() {
 		// do not do copy(chans, chans[1:]), since this may be quite slow
 		// for multi-million concurrent connections. Just move chans
 		// pointer one position ahead.
+		chans[0] = nil
 		chans = chans[1:]
 		wp.workersCount--
 	}