restful conn Ping should verify a connection

[hcwang512]

currently restful conn do nothing in Ping function. Both Open and Ping function will not verify the connection. It breaks the conventional process described in database/sql standard library。 I suggest to verify the connection in Ping function to stay the same with standard library. Below is the comment from database/sql Ping function. // Ping verifies a connection to the database is still alive, // establishing a connection if necessary. // // Ping uses context.Background internally; to specify the context, use // PingContext.

[hcwang512]

[huskar-t]

@hcwang512 Do you have any good advice?