【Unity】RandomRangeInt can only be called from the main thread.

using UnityEngine;

public class Player : MonoBehaviour
{
    private int mValue = Random.Range( 0, 10 );
}

このように変数初期化子でRandom.Range関数を使用すると
下記のようなエラーが発生します

RandomRangeInt can only be called from the main thread.
Constructors and field initializers will be executed from the loading thread when loading a scene.
Don't use this function in the constructor or field initializers, instead move initialization code to the Awake or Start function.

変数の初期化でRandom.Range関数を使用したい場合は
Awake関数やStart関数で呼び出す必要があります

using UnityEngine;

public class Player : MonoBehaviour
{
    private int mValue;

    private void Awake()
    {
        mValue = Random.Range( 0, 10 );
    }
}