This mod removes the need of air blocks when spawning a creature with structure-based system.
gif that compares the mod's witherfix feature with vanilla minecraft
gif that compares the mod's golemfix feature with vanilla minecraft
(The block in question now can be any block)

The mod also tries to spawn the golem in a safe position.
gif that shows vanilla minecraft golem suffocation when spawning it nearby a wall
gif that shows the golem teleporting far enough to avoid being affected by suffocation when spawning
gif that shows the golem breaking blocks to avoid being affected by suffocation when spawning
Because of the golem's hitbox, it can be suffocated as soon as it spawns if it is next to a wall or blocks at head height. So there are two options you can choose to avoid this.

These features can be enabled/disabled as you want in the config file, and yes, both can be enabled:
gif that shows both teleporter and blockbreaker mechanics at the same time

The mod allows the golem to do the following:
1» Be inmune to suffocation until the golem hits the ground, so lets the code wait until it's useful.
2» Teleport to the best direction (also corners), where fewer blocks are.
3» Break those blocks if needed.
(The golem will ignore directions with unbreakable blocks and do nothing if there are only unbreakable blocks.)

Wither & Golem Spawn Fix

📖About Wither & Golem Spawn Fix