This pull request introduces a comprehensive example setup for OpenTelemetry instrumentation and logging, including new middleware for HTTP tracing, example configuration files, and improvements to logging utilities. The changes provide a ready-to-use demonstration environment and enhance observability features in the codebase.

New Example and Observability Infrastructure:

• Added a complete example environment in the example/ directory, including a compose.yaml for running OpenTelemetry Collector, Prometheus, and Jaeger, configuration files for each service, and a sample server.go demonstrating HTTP tracing and logging integration. [1] [2] [3] [4] [5]

Tracing and Metrics Middleware:

• Introduced a new middleware.go implementing HTTP middleware for OpenTelemetry tracing, metrics, and structured logging. This middleware supports options for controlling cardinality, debug paths, and allowed headers.

Logging Utility Enhancements:

• Improved logger context handling in logger.go by refactoring context logger retrieval and adding support for extracting loggers directly from HTTP requests. Also renamed NewContextLogger to NewContextWithLogger for clarity. [1] [2] [3]

Dependency Updates:

• Updated dependencies in go.mod to newer versions for several packages, including prometheus/common, prometheus/procfs, and go.opentelemetry.io/proto/otlp. Added github.com/google/uuid as a direct dependency. [1] [2]

Linting Configuration:

• Enabled the varnamelen linter in .golangci.yml to enforce variable name length standards.