Useful packages

The standard libary of Go includes a huge number of packages. It is veryenlightening to browse the $GOROOT/src directory and look at thepackages. We cannot comment on each package, but the following are wortha mention: 11

  • fmt

  • Package fmt implements formatted I/O with functions analogousto C’s printf and scanf. The format verbs are derivedfrom C’s but are simpler. Some verbs (%-sequences) that can be used:

    • %v, the value in a default format. when printing structs, the plus flag (%+v) adds field names.
    • %#v, a Go-syntax representation of the value.
    • %T, a Go-syntax representation of the type of the value.
  • io

  • This package provides basic interfaces to I/O primitives.Its primary job is to wrap existing implementations of such primitives,such as those in package os, into shared public interfaces thatabstract the functionality, plus some other related primitives.

  • bufio

  • This package implements buffered I/O. It wraps anio.Readerorio.Writerobject, creating another object (Reader or Writer) that also implementsthe interface but provides buffering and some help for textual I/O.

  • sort

  • The sort package provides primitives for sorting arraysand user-defined collections.

  • strconv

  • The strconv package implements conversions to and fromstring representations of basic data types.

  • os

  • The os package provides a platform-independent interface to operatingsystem functionality. The design is Unix-like.

  • sync

  • The package sync provides basic synchronization primitives such as mutualexclusion locks.

  • flag

  • The flag package implements command-line flag parsing.

  • encoding/json

  • The encoding/json package implements encoding and decoding of JSON objects asdefined in RFC 4627 [RFC4627].

  • html/template

  • Data-driven templates for generating textual output such as HTML.

Templates are executed by applying them to a data structure. Annotations inthe template refer to elements of the data structure (typically a field ofa struct or a key in a map) to control execution and derive values to bedisplayed. The template walks the structure as it executes and the “cursor”@ represents the value at the current location in the structure.

  • net/http

  • The net/http package implements parsing of HTTP requests, replies,and URLs and provides an extensible HTTP server and a basicHTTP client.

  • unsafe

  • The unsafe package contains operations that step around the type safety of Go programs.Normally you don’t need this package, but it is worth mentioning that unsafe Go programsare possible.

  • reflect

  • The reflect package implements run-time reflection, allowing a program tomanipulate objects with arbitrary types. The typical use is to take avalue with static type interface{} and extract its dynamic typeinformation by calling TypeOf, which returns an object with interfacetype Type. See , Section .

  • os/exec

  • The os/exec package runs external commands.