Update websocket.h function "void do_read()"

[nowgoing]

Reason for update:

When state_ == WebSocketReadState::Payload, The function async_read_some() is not guaranteed to read all the data.
When remaining_length_ != 0 , you need to continue reading.

[mrozigor]

Can you write UT to show that problem exists? Because it looks like state isn't changed from WebSocketReadState::Payload, when remaining_length is different than 0. So it looks like staying in mentioned state up to point, when length equals 0.

[nowgoing]

Add test code print log

The log output is as follows

When remaining_length_ != 0 , websocket will stop reading.

[mrozigor]

But it's weird that moment earlier same amount of data are read at once.

[nowgoing]

So async_read_some() is not guaranteed to read the message data;The above problem occurs when binary audio data is transmitted using WebSocket, with 25 packets per second。

[mrozigor]

That's true. But you can only add else block, without assigning state_ variable.

[mrozigor]

Thanks! I've merged it to my fork :)