1. 1. Logging
2. 1. 1.1. Getting started with logging in Rust
   2. 1.2. Simple Logger new
   3. 1. 1.2.1. Simple Logger new
      2. 1.2.2. Simple Logger init
      3. 1.2.3. Simple Logger level
   4. 1.3. Logging with log4rs
   5. 1.4. env_logger
   6. 1. 1.4.1. env_logger in a simpl way
      2. 1.4.2. env_logger with Builder
3. 2. Tracing
4. 1. 2.1. Tracing demo
   2. 2.2. Tracing in a library
   3. 2.3. Tracing in an application
   4. 2.4. Simple tracing configuration with RUST_LOG environment variable