false positive in checking connection liveness

[lrita]

Issue description

Tell us what should happen and what happens instead

#934

When I update this package version to d0a5481, it alway show follow error log. After a simple investigation, I think there should using SyscallConn.Control instead of SyscallConn.Read in connCheck. If there is no data in the socket, we maybe got a reading-timeout error when driver do a connection liveness checking by using SyscallConn.Read. @vmg , do you think so? Thanks.

Example code

dsn: 

charset=utf8&parseTime=True&loc=Local&timeout=1s&writeTimeout=3s&readTimeout=3s

Error log

the package always logging:

closing bad idle connection: raw-read tcp xxx.xxx.xxx.xx->xxx.xxx.xxx.xx: i/o timeout

Configuration

Driver version (or git SHA):
d0a5481
Go version:
go1.12.4
Server version:
MySQL 5.5.31
Server OS:
Centos 7.0

[vmg]

Hiii @lrita! Thanks for the report! I think I've spotted the issue -- could you try out #964 to see if it fixes your problem?

[lrita]

After testing, this patch works fine. Clear the read-timeout flag of connection by SetReadDeadline is fine also. Good job.

[vmg]

🙇