title: sql.DB.Ping() not returning error when DB is down
body: <p>I intentionally stopped the database after successfully launching my Go program to test the behavior of sql.DB.Ping().</p>
  
  <p>sql.Open is being called in init()</p>
  
  <p>Much to surprise, sql.DB.Ping() did not return an error when my program called it before calling sql.DB.Query().</p>
  
  <p>Why am I doing this?
  Just trying to write robust code. Checking the integrity of the DB connection only at startup may not be sufficient for a long-lived production web application.</p>