Goroutine leak with latest "cancelable stdin" changes

[knz]

See: https://circleci.com/gh/cockroachdb/cockroach/22259

This prevents us at CockroachDB from upgrading to the latest readline.

The problem is that the global var Stdin is set to a CancelableStdin object but this object is never closed, so there is a goroutine remaining when the program using readline terminates. This makes leak checkers unhappy.

The better solution would be to create an API for readline to "initialize" and "finalize" the entire library. The CancelableStdin object would be created in "initialize" and closed in "finalize". This way, if a program (like cockroach) merely imports the readline package but does not actually use it, there will be no goroutine created.

[chzyer]

Also, add defer ins.Close() here should fix this.
https://github.com/cockroachdb/cockroach/blob/master/cli/sql.go#L247

[knz]

Thanks for the hint. However the failure was unrelated to the sql client, it occurs also when we run a Go test for the cli package. The leak occured because cli links to readline and the ioloop goroutine was started even if the test didn't use readline.

[chzyer]

I knew that, so I fix that in #77, but I just have a better fix in #78.
You can check the diff in here.
And, It also needs you add defer ins.Close() in sql.