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)
You can use the following steps to download it as a Kindle book. Download the pdf to your computer. Log into your Amazon Account and click on the Account and Lists arrow under your greeting on the top line. On the next page look for the box titles Digital content and Devices (it is a list of page titles. Click on Content and Devices in that list. Just under the black headings is a Line that says Manage your Content and Devices Content Device Preferences and Personal Privacy. Click on Preferences. At the bottom you will find a section Personal Document Settings. The last section is Approved Personal Document Email list. If your email address is not on there use the Add a New Email Address link to add it to the list (this ensures only you can add documents to your account). Go to your Kindle device and under More find Settings. Under Send-To-Kindle email address you will find your device's personal email address. Email the downloaded pdf file to that email address from the email address you added to your account (no subject needed). You will get a notification from Amazon that the document is in your library. Under the More option on your Kindle Sync your device and the book will appear in your library.
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.