What if Trump changes his mind?

The thought occurs to me. Here goes . . .

Donald Trump has said he wants special counsel Robert Mueller’s report on alleged collusion, conspiracy and obstruction of justice to be made public. The president said he doesn’t object to the public seeing what Mueller produces.

But the president is known to change his mind. Sometimes on a whim. On a dime. Without warning.

What might happen if after seeing an outline of the report’s findings the president changes his mind? Suppose he calls Attorney General William Barr and instructs the AG to keep the report from Congress. Don’t release it to the public.

My question: Would such an act constitute an impeachable offense?