support logger when querying database

[nullne]

No description provided.

[coveralls]

Coverage decreased (-1.2%) to 86.782% when pulling 39066c3 on nullne:master into 34fba28 on linxGnu:master.

[linxGnu]

@nullne IMHO, I think mssqlx should be as thin and dependency-less as possible.

In this way, I think we should not inject logging this way. How about letting user overwrite DB instantiation. For example:

type Instantiate func(driver, dsn string) (*sql.DB, error)

type clusterOptions struct {
   ...
   instantiate Instantiate
}

func WithInstantiate(f Instantiate) Option {
        return func(o *clusterOptions) {
                o.instantiate = f
        }
}

var db *sql.DB
if opts.instantiate != nil {
        db, err = opts.instantiate(driverName, masterDSNs[mId])
} else {
        db, err = sql.Open(driverName, masterDSNs[mId])
}

if err != nil {
    return
}

dbConn := sqlx.NewDb(db, driverName)

In this way, user could instrument db instantiated as he wishes in anyway he want:

db, err := mssqlx.Open(...., WithInstantiate(driver, dsn string) *sql.DB {
    logger := ....
     ...
     db := sqldblogger.OpenDriver(
					masterDSNs[mId],
					dbConn.Driver(),
					logger, loggerOptions...
      )
      return db
})

[linxGnu]

@nullne ptal: #9

[nullne]

it works, thank you very much @linxGnu