modernizes for loop in cmd/, internal/ (#21309)

internal/grid/connection.go

@@ -1041,7 +1041,7 @@ func (c *Connection) readStream(ctx context.Context, conn net.Conn, cancel conte
 		// Handle merged messages.
 		messages := int(m.Seq)
 		c.inMessages.Add(int64(messages))
-		for i := 0; i < messages; i++ {
+		for range messages {
 			if atomic.LoadUint32((*uint32)(&c.state)) != StateConnected {
 				return
 			}

internal/grid/debug.go

@@ -143,7 +143,7 @@ func (t *TestGrid) WaitAllConnect(ctx context.Context) {
 }
 
 func getHosts(n int) (hosts []string, listeners []net.Listener, err error) {
-	for i := 0; i < n; i++ {
+	for range n {
 		l, err := net.Listen("tcp", "127.0.0.1:0")
 		if err != nil {
 			if l, err = net.Listen("tcp6", "[::1]:0"); err != nil {

internal/grid/muxclient.go

@@ -574,7 +574,7 @@ func (m *muxClient) ack(seq uint32) {
 		return
 	}
 	available := cap(m.outBlock)
-	for i := 0; i < available; i++ {
+	for range available {
 		m.outBlock <- struct{}{}
 	}
 	m.acked = true

internal/grid/muxserver.go

@@ -130,7 +130,7 @@ func newMuxStream(ctx context.Context, msg message, c *Connection, handler Strea
 	// Fill outbound block.
 	// Each token represents a message that can be sent to the client without blocking.
 	// The client will refill the tokens as they confirm delivery of the messages.
-	for i := 0; i < outboundCap; i++ {
+	for range outboundCap {
 		m.outBlock <- struct{}{}
 	}