Add support for resp3 protocol

[monkey92t]

1. Support redis RESP3 protocol, can work under RESP2 and RESP3.
2. If redis-server version >=6.0, RESP3 protocol is enabled by default. Otherwise use RESP2 protocol (redis < 6.0).
3. Remove test Subscribe __redis__:invalidate, it only works in RESP2 mode(redis6.0+).
4. $EOF:<40 bytes marker><CR><LF> and *?<CR><LF> that have not been enabled by redis-server have not been implemented for the time being, they will be followed up in the future.

[vmihailenco]

If redis-server version >=6.0, RESP3 protocol is enabled by default. Otherwise use RESP2 protocol (redis < 6.0).

It looks like the code always uses https://redis.io/commands/hello to switch to RESP3. And HELLO is only available since v6.0.0. So I guess v9 branch

• does not support Redis < 6.0
• always uses RESP3

Which is fine - I just want to confirm my understanding.

[monkey92t]

If redis-server version >=6.0, RESP3 protocol is enabled by default. Otherwise use RESP2 protocol (redis < 6.0).

It looks like the code always uses https://redis.io/commands/hello to switch to RESP3. And HELLO is only available since v6.0.0. So I guess v9 branch

• does not support Redis < 6.0
• always uses RESP3

Which is fine - I just want to confirm my understanding.

If conn.HELLO(ctx, 3) fails to execute (redis<6.0), there will be no error, and it will continue to use RESP2 to execute commands.
If redis-server >= 6.0, HELLO is executed successfully and RESP3 is used.

In redis5 or lower version, it can work normally.

[vmihailenco]

Awesome, thanks.