Goering waited until the morning before he was to hang. According to the Wikipedia:
Unwanted by his former colleagues and hunted by the Allies, Himmler attempted to go into hiding. He had not made extensive preparations for this, but he had equipped himself with a forged paybook under the name of Sergeant Heinrich Hitzinger. With a small band of companions, he headed south on 11 May to Friedrichskoog, without a final destination in mind. They continued on to Neuhaus, where the group split up. Himmler and two aides were stopped at a checkpoint on 21 May and detained. Over the following two days he was moved around to several camps, and was brought to the British 31st Civilian Interrogation Camp near Lüneburg on 23 May. The duty officer, Captain Selvester, began a routine interrogation. Himmler admitted who he was, and Selvester had the prisoner searched. He was taken to the headquarters of the Second British Army in Lüneburg, where Doctor Wells conducted a medical exam. The doctor attempted to examine the inside of Himmler's mouth, but the prisoner was reluctant to open it and jerked his head away. Himmler then bit into a hidden cyanide pill and collapsed onto the floor. He was dead within fifteen minutes. Shortly afterward, Himmler's body was buried in an unmarked grave near Lüneburg. The precise location of the grave remains unknown.
 The body of Heinrich Himmler lying on the floor of British 2nd Army HQ after his suicide on 23 May 1945 |