What are build tags in Go?

Build tags (also called build constraints) conditionally include or exclude a file from compilation. The modern syntax (Go 1.17+) uses a comment at the top of the file: //go:build linux && amd64. Boolean operators (&&, ||, !) and parentheses are supported. Common uses: OS-specific implementations (//go:build windows), architecture-specific code, including integration test files only with a specific tag (//go:build integration), and excluding files that depend on unavailable native libraries. Run go build -tags integration ./... to include tagged files.