Letters to God (2010)

A young boy fighting cancer writes letters to God, touching lives in his neighborhood and inspiring hope among everyone he comes in contact. An unsuspecting substitute postman, with a troubled life of his own, becomes entangled in the boy's journey and his family by reading the letters. They inspire him to seek a better life for himself and his own son he's lost through his alcohol addiction.

Unfortunately the movie Letters to God is not yet available on HBO Max.