2. The toolchain and workspace

2.1 The commands you'll type every day

Command	What it does
`go run .`	Compile to a temporary binary and run it
`go build`	Produce a binary for the current OS/arch
`go test ./...`	Run every test in the module
`go vet ./...`	Static analysis for correctness bugs (e.g. `Printf` format mismatches)
`go fmt ./...`	Reformat every file to the one canonical style
`go mod init <module>`	Start a new module, write `go.mod`
`go mod tidy`	Add missing requirements, remove unused ones
`go get pkg@version`	Add/upgrade a dependency
`go install pkg@version`	Build and install a binary into `$GOPATH/bin`
`go doc pkg.Symbol`	Read documentation without leaving the terminal

2.2 Modules, not GOPATH

Pre-2019 Go required your code to live inside $GOPATH/src. Modules (go.mod) decoupled that: any directory can be a module root. go.mod pins your module's own import path and its dependencies' versions; go.sum pins their cryptographic hashes so a build is reproducible even if a dependency's tag is force-pushed upstream.

// go.mod
module github.com/kumaran/toolbelt

go 1.22

require (
	github.com/spf13/cobra v1.8.0
)

2.3 Cross-compilation, usually simple for pure-Go code

Go's compiler targets are selected with two environment variables, and pure-Go programs usually do not need a separate compiler toolchain per target. If your build uses cgo, native libraries, or OS-specific files, you may need a matching C cross-compiler and target libraries.

GOOS=linux   GOARCH=amd64 go build -o toolbelt-linux-amd64 .
GOOS=darwin  GOARCH=arm64 go build -o toolbelt-mac-arm64  .
GOOS=windows GOARCH=amd64 go build -o toolbelt.exe        .

2.4 Real-world example

A pure-Go CLI you build on your Apple Silicon laptop, tested with go test ./..., can often be cross-compiled into a Linux amd64 binary and dropped into a small container image with no language runtime dependency — no python3, no node_modules, no JVM. This deployment story is one reason so much infrastructure tooling (Docker, Kubernetes, Terraform, Prometheus) is written in Go.