Modify README to note runtime.LockOSThread() is needed.
Modify README to note runtime.LockOSThread() is needed.

Fix missing runtime.LockOSThread() in example code.

jonbuckley33/glfw3,gonutz/glfw,go-gl/glfw,gonutz/glfw,go-gl/glfw,james4k/glfw,go-gl/glfw,jonbuckley33/glfw3,james4k/glfw