Logrus

Logrus is a structured, pluggable logging library for the Go programming language. It originated as an extension of the standard library’s log package and was created by Sirupsen in 2014. Since then it has become a widely used choice for Go projects due to its flexible formatting, leveled logging, and extensible architecture. The project is hosted on GitHub under the module path github.com/sirupsen/logrus and is released under the MIT license.

The library provides two core constructs: Logger and Entry. A Logger manages configuration and outputs, while an Entry represents a log event with a set of fields. Log messages are emitted with a chosen severity level, such as Panic, Fatal, Error, Warn, Info, Debug, or Trace. Structured logging is supported through fields added with WithFields or WithField, enabling rich, contextual data to accompany log messages.

Output formatting is handled by formatters, notably TextFormatter and JSONFormatter. JSONFormatter is useful for machine parsing and centralized logging, while TextFormatter offers human-readable logs with optional colorization. Logrus also supports hooks, which allow log events to be augmented or routed to multiple destinations, such as external services or files. It can be configured to write to an io.Writer and can integrate with the standard library’s log package via adapters.

Logrus remains active in the Go ecosystem and is widely used in various projects, including Docker-related tooling. It competes with other Go logging libraries like zap and zerolog, offering a balance of usability, structure, and extensibility.