Hopefully you can find some useful coaching materials from the following links:
Horst Wein's Key to Better Hockey - a coaching pdf text book for young hockey players from 7 to 14 (but you can use these concepts and exercises successfully with all age groups)
Portrane Hockey Club - A large collection of training material from the UK and Australia including GK training material.
Coach Shiv - FIH coach Shiv Jagday's YouTube Channel which includes coach education videos covering the various topics of the game
Instagram - For individual skills see Leap Hockey or Kinger Hockey. Please be careful in what skills training you choose to follow on Instagram. I have watched a "top" player "teaching" people how to hit a backhand shot and hitting more than 10 hits in succession with the back of the stick. These two I have mentioned consistently give excellent advice and have some really good exercises that can often be done in your back yard.
Preseason Training - A personal structured regime to get fit for Hockey in up to 16 weeks from being completely unfit (can't do 100m in 30 secs unfit!). If the beginning weeks are too easy, jump in at a distance and time you feel will push you but not exhaust you. You are not supposed to feel as though you are going to die at any point in this programme, but you are supposed to feel good about achieving the goals you have set yourself. The fact you are getting fitter is an added bonus.