When a player puts wheat in their hand while a goat tries to ram into them, it will stay in 'ram mode' and walk at high speed (similar to a player walking on ice with a speed effect) as long as it is attracted to the wheat. When the goat is no longer attracted to the wheat (i.e. it becomes too far to see the player holding the wheat) it behaves normally once again.

To reproduce, have wheat in hotbar.

After the goat chooses to ram you, it performs an animation (this should help you prepare to switch the item in your hand).

As soon as the goat starts charging towards you, select the wheat in your hotbar. (From my one experience) the goat will continue to charge around the player until it is no longer attracted to the wheat.