Standard library

The standard library is source-distributed with the toolchain. Packages compile with the application, while operations that require the operating system, network, clock, process, or browser are provided through governed runtime and host contracts.

Core packages#

• errors, fmt, strconv, and strings cover errors, formatting, conversions, and text.
• bytes, unicode, and unicode/utf8 cover byte and Unicode processing.
• cmp, maps, slices, and sort provide common collection operations.
• math, math/bits, and math/rand provide numerical helpers.
• regexp provides regular-expression compilation and matching.

Encoding#

• encoding/json encodes and decodes typed values and open dynamic values.
• encoding/toml handles TOML configuration data.
• encoding/base64, encoding/hex, and encoding/binary cover binary interchange.
• encoding/csv reads and writes row-oriented text data.

Prefer typed structs for stable schemas. Use any and the dyn package when a schema is intentionally open.

I/O, files, and processes#

• io, io/fs, bufio, and bytes define stream, filesystem, buffering, and in-memory byte contracts.
• os, path, and path/filepath expose host filesystem and path behavior.
• os/exec starts governed child processes on hosts that grant the capability.
• flag parses command-line flags.
• log supplies structured application logging primitives.

Host-dependent functions can report unsupported capability on sandboxed targets. Libraries should accept interfaces such as readers, writers, and filesystems so callers can provide deterministic test implementations.

Network and URLs#

• net defines addresses and connection-level contracts.
• net/http supplies HTTP request, response, client, and server behavior where the host supports it.
• net/url parses and constructs URLs.

Browser networking remains subject to origin and host policy. Desktop and embedded hosts should grant the narrowest authority needed by the application.

Time, context, and synchronization#

• time provides instants, durations, timers, and formatting.
• context carries cancellation, deadlines, and request-scoped values.
• sync provides synchronization primitives for supported shared-runtime scenarios.
• Channels remain the preferred coordination primitive between goroutines in one island. Ports carry messages across islands.

Runtime packages#

• runtime exposes scheduler and runtime information intended for application use.
• runtime/mem exposes bounded memory observations and controls where the backend contract permits them.
• toolchain exposes versioned toolchain facts to governed generators and build integrations.
• dyn defines the dynamic-access protocol and stable error categories.

Portability#

Package presence alone does not grant a platform effect. The same API can be implemented by a native provider, a Web host import, a deterministic test provider, or an unsupported-capability response. Check errors and declare UI platform requirements in the application manifest.

The maintained package source lives under lang/stdlib. Its tests in tests/lang are the executable compatibility contract across VM, JIT, GC stress, Native AOT, and Wasm VM lanes.