1. writing chunks directly to disk instead of buffering in memory
2. using fixed-size buffers (32KB) for all I/O operations
3. optimizing buffer allocation strategy in downloadInMemory
4. implementing proper file synchronization with mutex locks
5. calculating chunk boundaries on-the-fly instead of pre-allocating
the memory profiling showed excessive allocations in bytes.growSlice
which has been addressed by minimizing intermediate buffers and
eliminating unnecessary memory copies
these changes should fix the observed OOM issues when downloading
large files while maintaining the same functionality
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