Just curious when does killua first use his godspeed technique ?

Godspeed (Kanmuru) is made up of two parts: Speed of Lightning/Volt-Speed (電光石火, Denkō Sekka), the ability to move his body according to his own will, used to travel long distances at high speed, and Hurricane Swift Thunder (疾風迅雷, Shippū Jinrai), the ability to sense his opponents movements and have his body react automatically, which he uses to evade enemy attacks with flawless speed and timing. Kanmuru can only be used for a short amount of time before needing to be recharged.