If I had to bet my own personal hard earned cash, it would be that President Trump does not "go to jail".
Willing to testify under oath is a far cry from your alarmist headline.
Realistically speaking, it is practically impossible to impeach a president, much less put one in jail.
Hell, President Clinton was caught dead to rights, committing perjury ON VIDEO, in stereo, and in full color.
He did not lose his job (impeachment) nor serve a second of jail time for a straight up felony when he found a handful of Republicans willing to put aside partisanship.
Trust me, if you or I did any of the crap these heads of state have done, they would throw us in jail and eat the key.