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🗓️ 26102024 1515

GO MODULES

Core Concept: Go modules are Go's dependency management system - each module is defined by a go.mod file that tracks dependencies and versions.

Initialize Module​

go mod init github.com/username/project

Creates go.mod:

module github.com/username/project

go 1.21

Adding Dependencies​

# Automatically adds to go.mod
go get github.com/go-chi/chi/v5

# Specific version
go get github.com/pkg/errors@v0.9.1

# Latest
go get -u github.com/pkg/errors

go.mod File​

module github.com/username/yiyu-backend

go 1.21

require (
    github.com/go-chi/chi/v5 v5.0.11
    github.com/go-chi/cors v1.2.1
)

go.sum File​

Checksums of dependencies (don't edit manually):

github.com/go-chi/chi/v5 v5.0.11 h1:BnpYbFZ...
github.com/go-chi/chi/v5 v5.0.11/go.mod h1:DslCQ...

Common Commands​

go mod tidy        # Add missing, remove unused
go mod download    # Download dependencies
go mod verify      # Verify checksums
go mod vendor      # Copy deps to vendor/
go get -u ./...    # Update all dependencies

Import Paths​

import (
    "fmt"                               // standard library
    "github.com/go-chi/chi/v5"         // external package
    "github.com/user/project/internal" // internal package
)

Module Versioning​

Semantic versioning: vMAJOR.MINOR.PATCH

go get github.com/pkg/errors@v0.9.1    # Specific version
go get github.com/pkg/errors@latest    # Latest
go get github.com/pkg/errors@v0.8.0    # Older version

Replace Directive​

For local development:

replace github.com/user/library => ../library

Exclude Directive​

exclude github.com/broken/pkg v1.2.3

Internal Packages​

project/
├── internal/      # Can't be imported by other projects
│   └── helpers/
└── pkg/           # Can be imported
    └── utils/

Go enforces: Other projects can't import from internal/

Best Practices​

  1. Commit go.mod and go.sum - Both are source files
  2. Run go mod tidy regularly - Keep dependencies clean
  3. Use semantic versioning - v1.x.x for stable APIs
  4. Pin versions in production - Don't use latest
  5. Vendor for reproducible builds - go mod vendor if needed
TIP

Run go mod tidy before committing to clean up unused dependencies.

References​