ErrorEqual compares Go errors for equality.

NewCallbackCloser returns a Closer that calls the provided function upon closing.

NewRoundTripCheckRequest creates a new instance of a type that implements http.RoundTripper, which before returning theResponse and theError, executes checkRequest against a http.Request.

NewTemporaryDirectory creates a new temporary directory for transient POSIX activities.

NilCloser is a no-op Closer.