Preheat oven to 350 degrees. Spray a 9X5 loaf pan and line with parchment paper.
In a small dish, combine flax with milk and stir well. Let sit at least 5 minutes.
In another small bowl, whisk together the flour, espresso powder, baking soda, salt, and cinnamon. Set aside.
In a large bowl, mash the bananas with a fork. Add flax/milk mixture, melted coconut oil, cane sugar, and vanilla extract. Stir until well combined.
Add dry ingredients to wet ingredients and mix until just combined. Fold in the chocolate chunks.
Transfer batter to loaf pan and bake for 50-55 minutes or until a toothpick inserted in the middle of the loaf comes out clean.
Let cool in pan for 10 minutes, then transfer to a cooling rack and let cool completely before slicing.