The lead comes off the hook and your dog starts bouncing. The walk is exciting, and every rushed departure has taught them that barking is part of the launch. You do not need to wait for a perfectly still dog before every walk, but you can make the first minute less frantic.
Check that the lead and harness fit comfortably. If your dog hides, freezes, or growls when equipment appears, that is a different problem from excited jumping, check for pain and introduce the equipment gently rather than insisting on a calm sit.
Practice when you are not leaving
Pick up the lead, reward a moment of four paws on the floor, then put it back. Repeat later. When that is easy, clip it on, reward, and unclip without opening the door. Move on to approaching the door, touching the handle, and opening it a crack, each in a short session. If your dog barks or leaps, make the next step simpler rather than standing there indefinitely with the walk withheld.
On a real walk, use the easiest version that works. Prepare treats and equipment beforehand, clip on in a quiet place, and reward your dog for walking with you through the doorway. Give them a chance to sniff soon after leaving. A few calm steps count more than a long performance at the threshold.
If your dog grabs the lead or your clothes and you cannot manage the exit safely, ask a qualified, reward-based trainer for hands-on help. A good walk begins with both of you able to get out the door without a scramble. For the walk skills that follow a calm doorway, see the everyday leash-walking guide, practise the gear routine when no one is rushing out
Sources: Dogs Trust: How to train your dog to be patient in doorways. Dogs Trust: How to train your dog to wear a harness.