Apple removed the hardware Escape key with the newly launched MacBook Pro. The Escape key is still readily available on the Touch Bar, but you might prefer a dedicated hardware key if your workflow uses Escape a lot.
With macOS Sierra 10.12.1, Apple has added the option to remap the Escape key to a hardware modifier button (Caps Lock, Control, Option or Command). This remapping feature isn’t new, but the latest macOS Sierra release is the first time you can attach an Escape action to a modifier key.
To remap, go to System Preferences > Keyboard. Click on the Modifier Keys button at bottom right corner. Click the drop down menu next to the modifier key to remap.
Caps Lock is generally the least used key thus is a good candidate to use it for Escape function.
Escape key mapping is only available in macOS Sierra, Apple is evidently building this feature for those using the new MacBook Pro with the Touch Bar.