Go Modules

Initialize a Module

Creating a new Go module:

# Initialize a new module
go mod init github.com/username/project

# Create a project with the current directory name
go mod init

Managing Dependencies

# Add a dependency
go get github.com/some/package

# Add a specific version
go get github.com/some/package@v1.2.3

# Add the latest version
go get github.com/some/package@latest

# Add a specific commit
go get github.com/some/package@1234abcd

# Update all dependencies
go get -u ./...

# Update to minor versions
go get -u=patch ./...

Working with go.mod and go.sum

# Tidy up dependencies (add missing, remove unused)
go mod tidy

# Verify dependencies
go mod verify

# Edit go.mod file
go mod edit -require=github.com/some/package@v1.2.3

# Print module dependencies
go list -m all

# View module graph
go mod graph

Versioning

# Major version upgrade (v2+)
import "github.com/user/module/v2"

# Releasing a new version
git tag v1.2.3
git push origin v1.2.3

Vendoring

Vendoring dependencies (storing them in your repository):

# Create vendor directory
go mod vendor

# Build using vendored dependencies
go build -mod=vendor

Workspace Mode (Go 1.18+)

Working with multiple modules:

# Create a workspace file
go work init ./module1 ./module2

# Add a module to workspace
go work use ./module3

# Replace a module in workspace
go work edit -replace example.com/mod=./localmod

Module Configuration

Example go.mod file:

module github.com/username/project

go 1.21

require (
    github.com/pkg/errors v0.9.1
    golang.org/x/text v0.3.8
)

replace github.com/pkg/errors => ../errors

exclude golang.org/x/net v1.2.3

Working with Private Repositories

# Configure Git for private modules
go env -w GOPRIVATE=github.com/mycompany/*,gitlab.com/myteam/*

# Using SSH instead of HTTPS
git config --global url."git@github.com:".insteadOf "https://github.com/"

Module Proxies

# Configure GOPROXY
go env -w GOPROXY=https://proxy.golang.org,direct

# Disable proxy
go env -w GOPROXY=direct

Best Practices

Use semantic versioning for module releases
Run go mod tidy before committing changes
Consider vendoring dependencies for deployment stability
Use replace directives for local development
Pin dependencies to specific versions for stability