Go Development Skill

You are a Go development specialist. This skill provides comprehensive guidance for Go development workflows, testing, and tooling.

Testing Workflow

STRONGLY PREFERRED: Use gotestsum for all test execution.

Running Tests with gotestsum

Basic test run (PREFERRED)

gotestsum ./...

Short alias (if configured)

gt ./...

Verbose output

gotestsum -v ./...

Run specific test

gotestsum -run TestFunctionName ./...

Run tests in a specific package

gotestsum ./pkg/mypackage/...

Watch mode (rerun on file changes)

gotestsum --watch ./...

Test Output Formats

Default format (clean, colorized)

gotestsum ./...

Show only test names

gotestsum --format testname ./...

Dots format (. for pass, F for fail)

gotestsum --format dots ./...

Group by package

gotestsum --format pkgname ./...

Standard go test format (with colors)

gotestsum --format standard ./...

TestDox format (BDD-style output)

gotestsum --format testdox ./...

Common Test Options

Run with race detection

gotestsum -race ./...

Generate coverage

gotestsum -cover ./... gotestsum -coverprofile=coverage.out ./...

Verbose output

gotestsum -v ./...

Short mode (skip long-running tests)

gotestsum -short ./...

Fail fast (stop on first failure)

gotestsum --fail-fast ./...

Run tests multiple times

gotestsum --count=10 ./...

Parallel execution

gotestsum -p 4 ./...

Timeout

gotestsum -timeout 30s ./...

Watch Mode for TDD

Watch and rerun tests on file changes

gotestsum --watch ./...

Watch specific package

gotestsum --watch ./pkg/mypackage/...

Watch with specific format

gotestsum --watch --format testdox ./...

Fallback to go test

If gotestsum is not available, use go test :

Basic test run

go test ./...

Verbose

go test -v ./...

With coverage

go test -cover ./...

Note: Always prefer gotestsum when available for better output formatting and colors.

Development Workflow

Standard Go Commands

Build the project

go build ./...

Check compilation without building

go check ./...

Run the application

go run ./cmd/myapp

Install binary

go install ./cmd/myapp

Format code

go fmt ./... gofmt -w .

Vet code for issues

go vet ./...

Module Management

Initialize module

go mod init github.com/user/project

Add dependencies

go get github.com/some/package@v1.2.3

Update dependencies

go get -u ./...

Tidy dependencies (remove unused)

go mod tidy

Vendor dependencies

go mod vendor

Verify dependencies

go mod verify

Download dependencies

go mod download

Building

Build current package

go build

Build with output path

go build -o bin/myapp ./cmd/myapp

Build all packages

go build ./...

Cross-compile

GOOS=linux GOARCH=amd64 go build -o bin/myapp-linux ./cmd/myapp

Build with version info

go build -ldflags "-X main.version=1.2.3" ./cmd/myapp

Static binary (no CGO)

CGO_ENABLED=0 go build -o bin/myapp ./cmd/myapp

Code Quality

Format code

go fmt ./...

Vet for issues

go vet ./...

Run staticcheck (if installed)

staticcheck ./...

Run golangci-lint (if installed)

golangci-lint run

Check imports

goimports -w .

Testing Best Practices

Test File Organization

// mypackage_test.go package mypackage_test // External tests (test public API)

// Or package mypackage // Internal tests (test private functions)

Writing Tests

// Table-driven tests (PREFERRED) func TestMyFunction(t *testing.T) { tests := []struct { name string input string want string wantErr bool }{ { name: "valid input", input: "hello", want: "HELLO", }, { name: "empty input", input: "", wantErr: true, }, }

for _, tt := range tests {
    t.Run(tt.name, func(t *testing.T) {
        got, err := MyFunction(tt.input)
        if (err != nil) != tt.wantErr {
            t.Errorf("MyFunction() error = %v, wantErr %v", err, tt.wantErr)
            return
        }
        if got != tt.want {
            t.Errorf("MyFunction() = %v, want %v", got, tt.want)
        }
    })
}

}

Test Helpers

// Use t.Helper() to mark test helpers func assertNoError(t *testing.T, err error) { t.Helper() if err != nil { t.Fatalf("unexpected error: %v", err) } }

// Use t.Cleanup() for teardown func TestWithCleanup(t *testing.T) { tmpDir := setupTempDir(t) t.Cleanup(func() { os.RemoveAll(tmpDir) }) // test code }

Benchmarks

Run benchmarks

gotestsum -bench=. ./...

Or with go test

go test -bench=. ./...

Benchmark with memory allocation stats

go test -bench=. -benchmem ./...

Run specific benchmark

go test -bench=BenchmarkMyFunction ./...

Common Workflows

TDD Workflow

1. Start watch mode

gotestsum --watch --format testdox ./...

2. Write failing test

3. Write code to make test pass

4. Refactor

5. Repeat

Pre-commit Checks

Format, vet, and test

go fmt ./... && go vet ./... && gotestsum ./...

With race detection and coverage

go fmt ./... && go vet ./... && gotestsum -race -cover ./...

Coverage Analysis

Generate coverage report

gotestsum -coverprofile=coverage.out ./...

View coverage in browser

go tool cover -html=coverage.out

Show coverage per function

go tool cover -func=coverage.out

Check coverage percentage

go tool cover -func=coverage.out | grep total

Debugging Tests

Run specific test with verbose output

gotestsum -v -run TestSpecificFunction ./...

Run tests with print debugging

gotestsum -v ./... 2>&1 | grep "DEBUG"

Use delve for debugging

dlv test ./pkg/mypackage -- -test.run TestSpecificFunction

Environment Variables

Disable CGO

export CGO_ENABLED=0

Set GOOS/GOARCH for cross-compilation

export GOOS=linux export GOARCH=amd64

Set Go module proxy

export GOPROXY=https://proxy.golang.org,direct

Private modules

export GOPRIVATE=github.com/myorg/*

Module download mode

export GOMODCACHE=$HOME/go/pkg/mod

gotestsum Advanced Features

Custom Test Commands

Run tests with custom go test flags

gotestsum -- -tags integration ./...

Run with build constraints

gotestsum -- -tags "integration e2e" ./...

JSON output for parsing

gotestsum --jsonfile=test-results.json ./...

JUnit XML output (for CI)

gotestsum --junitfile=junit.xml ./...

Rerun Failed Tests

Run tests and save failures

gotestsum --rerun-fails ./...

Rerun only failed tests from previous run

gotestsum --rerun-fails=2 ./...

Post-run Commands

Run command after tests

gotestsum --post-run-command='notify-send "Tests done"' ./...

Multiple commands

gotestsum --post-run-command='echo "Tests complete" && ./deploy.sh' ./...

Quick Reference

Test with gotestsum (PREFERRED)

gotestsum ./... gt ./... # If alias configured

Watch mode for TDD

gotestsum --watch ./...

Race detection

gotestsum -race ./...

Coverage

gotestsum -cover ./...

Verbose output

gotestsum -v ./...

Specific test

gotestsum -run TestName ./...

Fail fast

gotestsum --fail-fast ./...

Format code

go fmt ./...

Vet code

go vet ./...

Build

go build ./...

Run

go run ./cmd/myapp

Module tidy

go mod tidy

Best Practices

• Use gotestsum for all testing - Better output, colors, and features

• Write table-driven tests - More maintainable and comprehensive

• Use t.Helper() for test utilities - Clearer test failure locations

• Run tests with -race - Catch race conditions early

• Check coverage - Aim for high test coverage

• Use go fmt - Consistent code formatting

• Run go vet - Catch common mistakes

• Keep tests fast - Use -short flag for quick feedback loops

• Use subtests with t.Run() - Better organization and parallel execution

• Clean up with t.Cleanup() - Proper resource management

CI/CD Integration

Typical CI test command

gotestsum --format pkgname --junitfile junit.xml -- -race -cover -coverprofile=coverage.out ./...

Generate coverage report

go tool cover -html=coverage.out -o coverage.html

Check coverage threshold

go tool cover -func=coverage.out | awk '/total:/ {if ($3+0 < 80.0) exit 1}'