ANSWER:
“Whoever asks Allah sincerely for martyrdom [Allahumma inni as’aluk ash-shahadah], Allah will cause him to reach the status of the martyrs even if he dies in his bed.”
We can also say the dua of Umar (may Allah be pleased with him) اللَّهُمَّ ارْزُقْنِي شَهَادَةً فِي سَبِيلِكَ ، وَاجْعَلْ مَوْتِي فِي بَلَدِ رَسُولِكَ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ )
رواه البخ