## Kotlin, 67 bytes ##
<!-- language: kotlin -->

    while(true)"|/-\\".map{print("\rLoading... $it");Thread.sleep(250)}

[![enter image description here][1]][1]

Fairly self explanatory, using `\r` to clear the line and taking advantage of Kotlin's awesome string interpolation.


  [1]: https://i.stack.imgur.com/FdSsE.gif