merkle tree library implemented in Go language.

• build tree when initialized
• proof whether a data block belongs to a merkle tree
• add block one by one, then build tree. (Useful when reads data incrementally from big files.)
• customize tree depth. (Default is binary tree. Depth depends on number of leaves.)
• consider whether use double hash

please see example.go

• wikipedia: merkle tree

• Go: 1.12.6