caarlos0/env
Env
env is a Go library that reads environment variables and populates the fields of a Go struct according to tag directives. It uses reflection to iterate over struct types and tags at runtime, mapping environment variable names to struct fields and applying parsing behavior defined in struct tags.
The library supports required field validation, returning errors when marked fields are missing or empty after parsing. It also provides default value fallback from struct tags when environment variables are not set, environment variable expansion that recursively substitutes references within values, and file content injection that reads file contents from paths specified in environment variables and assigns them directly to struct fields. Users can register custom parser functions to convert strings into arbitrary Go types during unmarshaling.
The project includes an API integration for fetching module and package details, listing module versions and packages, and searching packages and symbols. It also provides pagination support for API responses and rate limiting to 40 queries per second per IP.
Features
- Environment Variable-Based Configuration - Reads environment variables and populates the fields of a Go struct according to tag directives.
- Environment Variable Validation - Marks a field as required or non-empty, causing an error if the variable is missing or blank.
- Custom Parser Registries - Registers custom functions to parse environment variable strings into any Go type.
- Variable Substitutions - Substitutes embedded environment variable references within a variable's value during parsing.
- Environment Variable Substitution - Recursively substitutes ${VAR} or $VAR references within environment variable values before assignment.
- Schema Default Values - Applies fallback values from struct tags when environment variables are missing or empty.
- Struct Tags - Uses Go struct field tags to map environment variable names and configure parsing behavior for each field.
- Reflection-Based Unmarshallers - Populates struct fields by iterating over types and tags at runtime using Go's reflect package.
- Required Field Enforcement - Checks for missing or empty environment variables after parsing and returns errors for required fields.
- Custom Parser Registries - Provides a registry for custom parser functions that convert environment variable strings to arbitrary Go types.
- Environment Variable File Injectors - Reads file contents from paths specified in environment variables and assigns them directly to struct fields.
- File-Based Loading - Reads the content of a file whose path is given by an environment variable and assigns it to the struct field.
- Configuration Management - Parses environment variables into structs.
- Configuration Management - Listed in the “Configuration Management” section of the Awesome Go awesome list.
- Configuration Management - Environment variable parser for structs.
Star history
How this analysis was created: This summary and feature list are AI-generated from collected project material and can contain mistakes. Stars, license and language are imported from GitHub. Inclusion does not mean that we have tested or audited this project. Check the source documentation for any feature you depend on. Learn more on our About page.
