TIL

Prevent dangerous struct copies with noCopy sentinel and go vet's copylock checker. Protect mutexes and sync primitives from value copies.

Pin tool versions in Go 1.24 with the new 'tool' directive. Replace tools.go pattern with native go.mod support for project tooling.

Test functions that write to stdout/stderr in Go by capturing output with os.Pipe. Learn patterns to avoid deadlocks in concurrent tests.

Understand why io.Reader takes a byte slice parameter instead of returning one. Learn about heap allocations and buffer reuse in Go streams.

Learn variable indirection in Bash with ${!var} syntax. Build context-aware configs, function dispatch, and dynamic variable name resolution.

Clean up pytest test signatures using @pytest.mark.usefixtures to inject implicit fixtures without autouse or unused parameter warnings.

Catch method override errors at type-check time with Python's @override decorator from PEP 698, preventing typos and signature mismatches.

Speed up Python module imports with __getattr__ from PEP 562 for lazy loading, deprecation warnings, and dynamic attribute access.

Master Docker mount types: volumes, bind mounts, tmpfs, and build cache. Clear syntax comparison between -v and --mount options with docker-compose.

Automate environment variables per directory with direnv. Load .envrc files on entry, unload on exit. Integrate with Python venv and uv workflow.

Master Bash namerefs with declare -n to create dynamic variable references. Build generic functions for arrays and associative arrays without eval.

Test HTTP requests in Python with pytest-httpx for full mocking, respx for pattern matching, or VCR.py for recording real responses.

Write readable parametrized tests with pytest.param for better test names, conditional skips, custom IDs, and structured test data.

Make raw HTTP requests with Bash's /dev/tcp file descriptor. Build health check scripts without curl or wget using TCP socket connections.

Replace mkdir, cp, and chmod with a single install command. Copy files, create directories, and set permissions in one step with GNU coreutils.