To be able to do this you need two people. One person must keep opening and shutting the door rapidly while the second person then mines the door. If done correctly you wil get another door with your original one still standing.
Easy Diamonds, Gold, Bloodstone:
If you travel 3,100 blocks away from Spawn you will be in this big rocky area where you will be able to easily find gold on the surface. Use iron to make an iron pickaxe to get the gold and then make a gold pickaxe to get diamond. Make a diamond pickaxe using diamond to get Bloodstone and use Bloodstone to make a Bloodstone pickaxe which can then be used to get more of whatever you desire. If you are playing Survival mode and you don't want more monsters to spawn and come after you the further you progress in the game you must set the game mode to 'No-Enemies'.
To do this cheat you need to fine a crater.I found mine at 743 in my world I don't about you tho.First get all the iron guns and get alot of bullets unless your on creative and then ether go to 743,1,000,or 2,000 and then eventually you will find a crater get your gun out and go down in the crater caves and find a alien,kill the alien and it for me it is a 99% chance the alien will drop diamonds when killed.