Long Ball Technique
Goalkeepers of all ages and skills have problems with their goal kicks for several different reasons but the biggest error I see keepers doing is caring too much about power and speed when it comes to striking the soccer ball from the six yard box. When you over focus power and speed you leave room for errors from mistiming your strike to losing balance on your plant foot.
It's all about technique and contact when it comes to the goal kick and if you're just a starting or beginner goalkeeper don't worry so much about distance focus on accuracy. I can promise you if you can accurately pass the ball a medium distance it is much better than just kicking it up in the air for a 50 /50 ball.